I know this subject has been beat to death, but I need it to be beat a bit more. I read that early manufacturers liked to shoot 2 5/8" shells in 2.5" chambers because they felt it gave a better seal and performance. I have also heard that 2.75" shells in 2.5" chambers can dangerously increase pressures and tear the edge of the shell off, while I have also read that the increase in pressure by doing so is not all that much, say 500 psi +/-. There's a lot of conflicting info out there. Bottom line: would a 7k psi low pressure 2.75" shell be dangerous in a 2.5" chamber Lefever? I am reloading 2.5" shells anyway, but I would like to know if I can shoot some of the shells I already have.

Bottom line for my pea brain Mark:
Will it increase pressure? (assuming the opened case mouth does NOT extend into the forcing cone) Maybe alittle.
Will it increase recoil? Likely and possibly alot.

Why in the world put your gun's 100 year old stock wood (and your rapidly aging shoulder and cervical spine) through the abuse when 2.5" shells are now readily available?

Why would it increase recoil and what do you mean ''alot''?

I'm thinking paper hulls would increase pressure more (because of being thicker) than a plastic hull would.

Pressure has nothing to do with recoil.

Using 2 3/4 low pressure shells in a 2 1/2 chamber will result in only a very moderate increase in pressure.

You can safely shoot your Lefever using those loads as long as the gun is in good shape.

Pete

I'm going to shoot some 2 & 3/4 Federal Vintage shells (advertised at 5000 psi) out of my 2 & 1/2" Scott hammer gun shortly if the rain holds off.

GJZ: I can personally testify that the recoil in my less than 6# 1928 20g Trojan with chambers 2 7/16" using factory 2 3/4" Win AA 7/8 oz. target loads was absolutely brutal, and obvious to everyone observing on the skeet field. The perceived recoil with 1 oz. 2 3/4" 1150 fps. 16g loads in my 2 9/16" chambered 6 1/2# LC 16g was clearly less after lengthening the chambers. 1 oz. 2 3/4" target loads in my 2 1/2" chambered No. 2 frame 12g Trojan weighing 7 3/4# felt no different than 1 oz. 2 1/2" shells.
But my anecdotal data may not apply to other's experience, as I have a terrible flinch and am very recoil sensitive.

"Bottom line: would a 7k psi low pressure 2.75" shell be dangerous in a 2.5" chamber Lefever? I am reloading 2.5" shells anyway, but I would like to know if I can shoot some of the shells I already have. "

Bottom line is, no one can tell you.
There are many opinions and in some cases back of the barn tests but as an Engineer I use the correct shells for the gun I am shooting.
It's really up to you and at your own risk.-Dick

Just my recollection of Bell's article, but I thought he said he tested paper hulls as well and they didn't show an increased pressure outside of the average of the plastic hulls. Also, my memory says that he got between 0 and 15% increased pressure from 2 3/4" shells in a 2 1/2" very short (1/2"???) forcing cone chamber.

My personal experience with only one load in a couple damascus guns is that my 2 3/4" Federal paper hull loaded to what a manual says should be mid 7K psi is actually coming out to mid 6K psi measured in a short chamber. I feel no significant recoil and velocities are super consistant at 1150 fps.

So, from all the above I've formed the opinion that short chambers (mainly 2 9/16 to 2 5/8" in American guns as I understand it) is not a reason to change my reloader setup to load 2 1/2" shells. It's inconvenient to change to shorter shells and I see no benefit at this time. However, if someone has convincing evidence that my information is wrong, I'm always willing to change that opinion.

I do have to take exception to the statement that pressure has nothing to do with recoil. I believe it is one of several key components in acceleration of the payload in a gun, the others being time and weight of the payload, and surface area of the payload upon which the pressure and time work to accelerate the payload and conversely, the gun in the opposite direction. I'm no physicist or ballistician, but I think that covers the basic physics of a gun. Sorry Pete.

We played with exactly that scenario this past weekend My 2 daughters, my son and I, ran through about 600 16 bore loads in 3 different doubles, a Stevens, a Cz and a "G" Lefever. We shot short shells in one bbl and LP handloads in the other, a number of times. All shooters tried the test. Which recoiled more? The short shells...in all guns.We all agreed on that. I dont know what chamber length my Lefever has. The load I am using is 1 oz shot, SG16 wads in both Fiochi and Federal/estate 2 3/4" plastic hulls.......pressure supposed to be under 7k, velocity 1220 fps...Non Scientific eval..FWIW

I wouldn't have expected more recoil from the shorter shells. Assuming similar light loads, why, please?

Thank you all for your opinions, which is all I can ask. Last Dollar, that's very interesting that the short shells recoiled more. Hmmm... Which powder are you using in your recipe and how many grains? I'm using Longshot, but may switch because it does produce the most recoil from what I understand. I agree with revdoc, that is hard on 100 yr. old wood.

I'll be heading to the range soon with a bunch of different 2.5" handloads and a few of the 2 3/4" lp shells and let you all know how it turns out. It will of course be an extremely scientific undertaking, using the most rigorous and statistical analysis available. I'm sure you all know what I mean

King, I wouldnt have a clue as to why we "perceived" less recoil, but we all seemed to. I dont think we can assume similar loads becsue I have no stats on the short shells ...Mark,I am loading 800x, you will have to consult your manual for the recipe...

As Pete said low pressue doesn't increase or dercrease recoil, velocity does. Now if you have a low pressure of 7000 psi and velocity of 1,050 the recoil will be less than 7000 psi and 1250 fps.
So really it should be stated low pressure, low velocity = low recoil.

Pete is correct in that pressure has nothing to do with recoil, period. If you increase pressure on a given load
AND that pressure increase also causes an increase in velocity, you might indeed experience some increased recoil. BUT, big BUT, the recoil increased because of the velocity increase, NOT because of the increased pressure. If shooting a long shell in a short chamber caused a pressure increase without a velocity increase, There would not be a recoil increase. OCYFTBAYWT (Of Course You're Free To Believe Anything You Want To. Sorry Chuck, I thought YOU knew better.

To measure actual recoil, you need to know the velocity of the projectile, the mass of the projectile, the mass of the charge and the mass of the gun.

To measure pressure, you also need to know the burn rate of the propellant, the size the chamber, the plasticity of the barrel, the size the bore, etc.

It is the simple physics.

Bell essentially showed that given a momentary constriction and the plasticity of a shot shell, pressure increase is negligible. But recoil did not change. Increasing the bore size immediately after the chamber will decrease the pressure some what, but again it does not affect recoil.

Pete

David,
As I posted; I believe pressure is one of several key components in what makes up recoil, not the only one. You can't have recoil without pressure. Sure, one can take the total ejecta and the MV and gun weight come up with a total energy of recoil. But that is a very simplistic answer that ignores the "time" element of recoil. It does not include answering what peak force is generated. And some have argued that peak force in recoil is irrelavent and maybe some think that peak force won't change if velocity and weight of ejecta doesn't change. Maybe. But, I don't believe that.

I think the point at which opinions start diverge is on the definition of the term "recoil". The simple definition is the total energy of the gun movement. That's not wrong. But there are other defineable elements like peak force and time of the forces. I believe peak force is an element of recoil that most shooters can feel. Others don't believe that. So, we disagree. That's o.k. it's just what I believe, not something everyone needs to believe.

I have shot both in my 2.5 Guns and have never noticed the difference in recoil or pressure signs on the primers. The S.Bell article is in the Winter 1992 DGJ if I remember right.

So if the ejecta slams into a retained wad just past the forcing cone, there will be no increase in the recoil before the barrel blows, compared to the ejecta exiting the barrel without obstruction? Took some physics once, and it was never very simple to me.

Chuck,
If my statement sounded like I was disagreeing with you, I was not. It is hard to believe that pressure, psi, which is force has nothing to do with recoil. In my opinion the force is going two ways forwards and backwards, and the backwards would be felt recoil. I know what people say but I have a problem trying to deal with the equation.
Still again my opinion, I reload 2 1/2" 20 ga. and 2 1/2" 16 ga. for short chambered "elsies" and I would not put 2 3/4" shells in it even though thousands have been fired that way.

To 'measure' recoil you will need to suspend the firearm from supports that will let it swing and know the weight of the gun and then measure the actual displacement during firing.


To 'measure' presure, you will need a transducer that is calibrated in a chamber connected to a recording device.

'Measurement' is not calculation which I believe you are discussing, PeteM.

To calculate recoil, the mass of the charge has no bearing and is not included if indeed it is calculable.
To calculate pressure, "the plasticity of the barrel" has no bearing and is not included.

It is not simple Physics. -Dick

You're talking about blowing up a barrel because of a stuck wad?
I've never had the pleasure. However, the answer to your hypothetical would be there would be little or no recoil because the ejecta never achieved any velocity, to speak of. You might need some clean shorts but not because of recoil.
You can have many times the allowable pressure and blow the gun to smithereens, while having no recoil at all. No ejecta velocity = no recoil. Further proof that pressure has nothing to do with recoil.

I think what PeteM is trying to state, which would be getting back to first principles and a simple approach, is that the sum of the Forces equals Zero(F(total) = 0). An increase of transverse forces could be attenuated or dampened by the strength of the tube while an increase in longitudinal down barrel(Fb+) force due to a higher velocity would be subject to a higher negative/reverse force depending on the friction factor(like a -kx spring factor) down the tube.

Also I failed to note that due to the geometry of the tube and if the tube is concentric the reflected/attenuated wave/vector collides with another reflected/attenuated wave at the center of the tube and cancels each other similar to a standing wave. If one of the transverse waves isn't reflected or only partially reflected from a weakened portion of the tube then the weakened portion experiences the opposite reflected wave which was to be cancelled.

Kind Regards,

Raimey
rse

Couple of notes. Total recoil is easily calculated from gun weight, ejecta weight, and ejecta average velocity via conservation of momentum and the relationship of kenetic energy to weight and velocity. Note that there is no pressure term. Now, felt recoil is not understood well enough to be defined. It could involve rearward force, rearward acceleration, or rearward velocity. Pressure acts over the area of the base of the wad and becomes force. The force from the pressure is unbalanced and results in acceleration of the payload. The acceleration results in velocity. As physics goes, that is pretty straight forward.

I am not aware of any data that correlates any of the above to felt recoil other than total recoil. Some people could conceivably feel components of the total recoil, but that is yet to be proven.

Pressire in an enclosed vessel has no recoil. So, pressure has influence on recoil only as it relates to rearward force, acceleration, or velocity.

If the barrel were plugged immediately ahead of the chamber, I doubt that normal powder charges could generate sufficient pressure for a chamber burst. An obstruction burst is a whole different phenom. It is caused when the high velocity gas behind the payload is forced to slow down as the payload strikes the obstruction and has to accelerate said obstruction to payload velocity. The gas slowdown results in a very high localized pressure known as a gas hammer. A gas hammer will, indeed, burst a barrel. A barrel burst is going to be violent on a loaclized level, but there will be no increase in recoil. Actually, recoil will be reduced unless the payload is alread at, or near, muzzle velocity.

I don't understand the "Note there is not pressure term" phrase. Pressure has to be a component as pressure is from the force of the expanding gas on a finite area at a static point in time(otherwise time varying because the volume is increasing)and is what starts it all. It's in there somewhere and I would say the effect of the bounding/excited molecules(kg) with a velocity(m/s^w)acting upon the finite area(m^2)of the base of the wad would give a force(N=kg m/s^2) but I don't have my units correct just yet.

Kind Regards,

Raimey

rse

I would be most concerned about compressing the shot in the column, by forcing it through a narrowed opening and therefore distorting it, would wind up blowing the pattern. I know for a fact, that lengthening the forcing cone improves patterns, so it only stands to reason the opposite would hurt.

binko

Two points: If the shot load hits an immovable obstruction in the bore there should be movement off the shoulder as the inertia of the moving load should be pushing the gun forward. However I doubt anyone notices it just as the barrel rips open.

Second point is if pressure itself produces recoil as Chuck believes then he should be able to also feel the barrels moving upward and downward at the same time in his hand as the pressure is acting with equal force in all directions. And with more surface area of the barrel sides involved than the area of the standing breech, he should feel more of this recoil in his forward hand than his shoulder.

I will stick with the law of physics and continue to believe recoil is a function of velocity produced.

REVDOCDrew I don't discount your antedotal incident. However, you need to compare equal velocity loads in both lengths (and blind so you don't know which is being fired) before the test would have any significance.

Don,
I am not aware of any data specific to that either. As far as being able to feel anything other than total energy from the recoil, I would say that I believe I can. That has yet to be proven though...conversely, it has yet to be disproven as well.

Jerry,
I believe you have misrepresented what I stated. I stated that it was a key component in producing recoil. That might seem subtle to you, but is a huge difference to how I would interpret the statement. I can't imagine how you'd make recoil in a gun without pressure, nor the other components I mentioned either. I believe they are inseparable in the real world.

What would you expect other than brutal recoil when shooting a 20 ga. gun weighing less than 6 pounds? Chopperlump

I consider firing 2 3/4" shells in shorter 2 5/8" chambers to be perfectly safe. And I'm in good company. I believe many gun manufacturers continued chambering their guns with the sort chamber and recommended using the longer shell. Here is a factory Parker hang tag for evidence. Note the chamber length and the shell length.

[img][/img]

I have no ides what any of the above means. I didn't see any mention of the items used in the recoil calculation formulas. There are a few around but most are similar and none include pressure, gauge of gun, bore I.D., forcing cone length or burning rate of the powder used. I have no problem accepting that the reason these are omitted is because they have no relevance.
If anyone believes that firing a 1 oz. load of shot, using a similar amount of the appropriate powder, at a given velocity, say 1200 fps., out of three 8 pound guns(12, 20 and 28 ga.) would produce anything other than the same recoil, you're beyond hope. Each shell would likely produce different pressures, 12 being least, then the 20 and the 28, the highest. Smaller bores routinely produce higher pressures. To say there would be no recoil without pressure is only true because there would be no velocity of the ejecta without pressure. If, as has been said before, the barrel was plugged so the ejecta could not move out the barrel, the pressure might be tremendous. But, there would be no recoil at all, because there was no movement of the ejecta to cause the corresponding reaction of the gun(recoil).

I do not have figures for what the closed cell pressure of a typical shotshell powder charge would produce, but I sincerely believe that if the shot charge "Failed to Move" the chamber of any ordinary gun would be "Blown to Smithereens".
Burrard gave some figures on this using the British bulk powder Smokeless Diamond, 33 grains = 3 dram measure.
This 33 grains if confined to a length of 1" of typical 2½" 12 gauge cartridge case would produce about 30.3 tons per sqin pressure. The pressure necessary to burst this typical chamber of good barrel steel having tensile strength of 40 tons per sq in would be 13.4 tons per sqin. Normal pressure for this load would be 2.8 tons.
Based on a 20 ton pressure yield strength (bbl would bulge, but not burst)it is necessary to go to about 4" before the strength of the steel excedes the maximum possible pressure capable of being generated.
All of this is based upon uniform pressure rise (No obstructional effect) for the 33 grain charge in that volume in which to expand.
This would tend to indicate that no ordinary gun could withstand a normal powder charge "IF" the shot failed to move.
This is WHY Burrard so strongly recommended "NO" shell be fired if it's "Loaded Length" allowed it to extend into the cone.
All other things being exactly equal even an extra deep crimp, requiring more force to open it can cause a drastic increase in pressure. If the loaded shell extends into the cone the opening of the crimp can be retarded causing an increase in pressure.
Max pressure is reached just after the shot begins to move & immediately begins to fall. As long as there is enough clearance for the crimp to open normally one would not really expect an increase in this max pressure. What one might well expect is a very slight slowing of the fall as it goes through the reduced dia. This would not be picked up on a normal pressure test which records only the max. It would show up if you had a trace of the pressure curve.
As to recoil the "Actual Recoil" is based solely on the mass ejected & the velocity at which it is ejected. I am at this point totally inclined to believe this amakes up about 98% of "Felt Recoil" with the remaining 2% composed of burn rates, cone shape, bore dias etc, etc, etc being of such small magnitude as to be undiscernable by Mere Humans.
There are numerous effects which can cause one to "Perceive" he has been "Kicked Harder" when in fact he has not. An example is wearing adequate ear protection can seem to "Take the Sting" out odf a "Hard Kicking" gun, but of course putting muffs over your ears does nothing to reduce either recoil or kick. An obnoxious odor from a particular powder could have a similar affect, but would not actually change the kick.
It is quite easy to get an idea in ones head, but until proven otherwise, Paint me Skeptic.

All of the elements of force, velocity have to be included as getting back to first prinicples, everything can be at least partially explained. Forget what you see, hear, feel and only consider what accurate sensors yield which can be put into a model describing the event and give quantifiable figures which really can't be argued like opinion can. Consider a group of billard balls in a circle with some type of force in the center. When all are excited, like a point source they travel in all directions with a similar velocity. Now consider the same billard balls arranged in a cylinder with finite depth and diameter and when the billard balls are excited, some go sideways while others press on forward along the path of least resistance. All have to encouter some type of reverse/negative force which seeds them to a steady state. The ones going to the sides are attentuated and reflected possibly colliding with another billard ball from the opposite direction forcing their velocity to zero. They may just be the entropy of the system but they have to be accounted for. From first principles, Force equals mass times acceleation(F=ma) and all systems strive to reach some sort of equlibrium(Thermodynamics) unless continually excited. Although I may have mixed wave and partical physics, either one should be able to expain the event. A combustion engine, a boiler, etc. are good examples and loosely are similar to what we have here with the wad be the piston which is being ejected. What we are looking for is how is the heat/expanding gas, whatever, converted into work.

Kind Regard,

Raimey
rse

I've been living a dillusional life or maybe I'm not a mere human, believing that recoil pads and gas guns facilitate a softer kick. And my handguns with their sights set up to point the muzzles downward, even they just don't recognize that they shouldn't be moving until the ejecta comes out of the barrel.

Using shot shells in chambers that are not the correct length for the shell


This question comes up innumerable times. Shotgun chamber length has changed many times over the last 100 years or so. There is for the 12 gauge 2”, 2&1/2”, 2&9/16, 3”, and 3&1/2” and I probably missed one.
In any event for various reasons individuals do not want to use the correct shell length. It may be due to availability, price or just plain lazy. These individuals search for a universal prescription that will allow them to use longer shells than the firearm was designed for. Some conduct ‘back of the barn tests’, publish the results in non-scientific journals and crow about themselves. These results are then accepted as a universal prescription, that this is indeed safe.
Some want to use standard factory loads, some low pressure loads whether factory or hand loads.
With myriad of firearms out there with different chambers, different steels, different heat treats, not to mention that many are of considerable age and have had ‘hard’ lifetimes not to mention who knows what type of refinish including heat treatment.
Couple that with the vast array of shot shells which includes the hull material, wads, powder and manufacturing techniques, it all leads to so many variations that no one can develop a universal prescription for all usage of longer shells in short chambers.
So, in effect, what you are doing when you use a shot shell not designed for your shotgun is a form of Proof Test each and every time you fire the shotgun.
SAAMI http://www.saami.org/ was tasked in 1926 by the Federal Government
• Creating and publishing industry standards for safety, interchangeability, reliability and quality
• Coordinating technical data
• Promoting safe and responsible firearms use
As such, this is what they say,

"UNSAFE ARMS AND AMMUNITION COMBINATIONS
The discharge of ammunition in a firearm that is not designed to shoot that ammunition can be dangerous and can result in serious injury or death to the user and/or bystanders, as well as damage to the firearm. This unsafe condition is caused by an excessive build-up and/or release of high-pressure gas in a firearm's chamber, barrel and/or action beyond which the firearm is designed to withstand. Therefore, in the interest of safety, you should use only ammunition of the caliber or gauge designated by the firearm manufacturer for use in that firearm. Markings indicating the correct caliber or gauge of ammunition to be used in a firearm are usually found on the firearm's barrel, frame or receiver.
One way to verify that you are using the correct ammunition is to check the head stamp on the ammunition to confirm that it matches the caliber or gauge markings placed on the firearm by the firearm's manufacturer. Some types of ammunition do not have markings on the head stamp of the cartridge. In that case, check the original ammunition packaging to determine its caliber. If you have any doubt about the caliber of the ammunition, you should not use the ammunition until you have it examined by a qualified person who can determine its caliber. Remember just because a round of ammunition can fit into a firearm's chamber, barrel or action does not mean it is safe to use that ammunition in the firearm.
Due to the availability of many different shapes and sizes of ammunition and firearms, there are countless unsafe ammunition-firearm combinations such that a comprehensive list of unsafe combinations is neither feasible, nor practicable. Below is a list of some unsafe combinations that are well known because of somewhat similar chamber and ammunition dimensions.
If the caliber or gauge is not clearly marked on the firearm, or if it appears the original markings on the firearm have been altered or modified in any way, do not use the firearm as serious injury or death could result to the user and/or bystanders, as well as damage to the firearm.
Similarly, SAAMI has not published voluntary recommended practices or procedures for re-chambering of firearms. It is possible the re-chambering of a firearm may not have been done properly or may not have been properly marked on the firearm. If the caliber or gauge marking is missing or altered in any way, you should not use the firearm. You should instead have the firearm examined by a qualified person to determine what caliber or gauge ammunition can safely be used in that firearm.
If you read the above closely, you can see that SAAMI also cannot give a universal prescription,
“Due to the availability of many different shapes and sizes of ammunition and firearms, there are countless unsafe ammunition-firearm combinations such that a comprehensive list of unsafe combinations is neither feasible, nor practicable.”

I have read all the above Posts, some are from knowledgeable individuals, some are plain drivel from Posters who know they Post drivel and some are from well intentioned individuals but not technically based.
None can supply a universal prescription to make your mind at ease when firing shot shells not designed for the shotgun in question.
The risk is yours.
Accept the risk and do what you want.
There is no easy way.-Dick
EOT

An 8 lb. SxS, O/U, and gas operated gun all receive the same recoil from a given load. Adding a recoil pad or shock absorbing type recoil reducer lets your body "feel" less of it because the total recoil is delayed getting to your shoulder. Ditto the gas gun. With a gas gun, the total recoil is broken up into 2 or 3 smaller punches. No argument. This is the difference of real "felt" or "perceived" recoil as compared to total recoil. It is deferent but, as always, the reason is within the bounds of the physics involved. Claiming differences in "felt" recoil due to different burning rates of the powder, lengthening forcing cones, overboring barrels, etc. are not likely to be true unless velocity is changed.

Great posts!

2-p makes some very good points on chamber pressure of a "solidly obstructed" breach. The other side is the 12-20 barrel burst scenario. Usually, the burst is at/near the point of obstruction, not at the breach. I think this can be calculated with the right data. I"ll look into it for the future.

"Total Recoil" is the kinetic energy or the gun on firing. It is easy to calculate if the factors are known, and they are easy enough to measure. It is the only thing I know of that correlates to what the shooter will feel when he fires the gun. It is not a 100% correlation; the difference is the subjective "felt recoil." I agree with Chuck that "felt recoil" is knowable, it is just that nobody has done the work.

Pressure contributes to recoil only as it generates velocity of the payload and powder gas. Pressure does not push back on the gun to cause recoil. Recoil is caused by conservation of momentum between the ejecta weignt and velocity and the gun weight and velocity. Recoil pads and recoiling parts within the gun don't change total recoil, but they do change the time span over which it is applied. This leads me to suspect that "felt recoil" is associated with force and/or acceleration of the gun.

Shot does not "slam into" the forcing cone or choke cone. It is at least semi-fluid and flows through these two constriction. The shot accelerates as it passes through constriction and the internal pressure drops (venturi principle). This is an orderly happening, which is why choke constriction works to reduce dispersiion.

Maybe I missed it, but I don't recall anyone saying "that they shouldn't be moving until the ejecta comes out of the barrel". "IF" they did they were wrong, recoil starts the instant the "Ejecta" starts to move. However, just for the fun of it lets assume you fire 1oz of shot, with a 35 grain (.08oz) wad over a 22 gr (.05oz) powder charge & assume the base of the wad has exactly 27" to move to the muzzle. Assume this fired from a 7lb (112oz) gun. Just as the base of the wad comes flush with the muzzle the powder gases will have filled the bore. While not absolutely correct it will be close enough for this scenario to take that half it's weight has moved the 27" length. Thus 1oz +.08oz +.025oz = 1.105oz. (1.105 x 27) ÷ 112 = .266. Thus at the instant the wad clears the muzzle the gun will have, in free recoil, moved .266". The rest of it's movement will be from the result of accumulated inertia. Now assume a standard target load velocity of 1200 fps. Even if there had been a totally uniform acceleration giving an average bbl velocity of 600 fps the charge would have traversed that 27" in .00375 sec. As acceleration is of course much more rapid nearer the chamber let's assume an average of 75% of acquired velocity or 900 fps It would then have a bbl time of .0025 sec. I have no doubt a change in acceleration rate of this magnitude would be readily felt, even though measured recoil would be identical for both. However this is a change in acceleration rate in excess of 30%. I have grave doubts that as long as the load was always adjusted to give this identical 1200 fps velocity, that any change one could make to internal bore dimensions or changes in powder burn rates, while maintaining a satisfactory load whould ever, & being extremely liberal, amount to a change as large as 5% in actual bbl time.
So small a change will require much thought & planning to even test & be certain that other external factors are not playing a more important role in what's "Felt" than an actual change in the recoil itself.

Excellent, 2-p!! I think we can add more to this model and refine it. Instantanious acceleration will be identical to instantanious pressure. Looking at time-pressure or displacement-pressure curves may give us a clue as to felt recoil. It may happen that we have to average pressure over some short time intervals to account for human reaction. Acceleration from a peak 7000 psi load is less than from a 9000 psi load.

Jumping around a bit here, since I'm multitasking on a telecon meeting right now, but...on the topic of pressure working against the base of the payload vs. working against the base of the shell/breach: Is there any reason to believe there is any difference in how this accelerates the payload and how/if it is the element that accelerates the shell head/breach aft? I've always believed that the pressure was the force acting in equal but opposite directions, one against the payload and the other against the shell head. Where else would the opposing force act against?

Chuck, have you ever shot shells without shot in them? Is pressure less than when they do have their corresponding shot load? Does the gun recoil the same as when there is shot in the shell?

JC

Drew, as Joe Wood's example of a Parker hang tag illustrates, it was not unusual for American gunmakers to recommend the use of longer shells in shorter chambers. In fact, as reported in a two-part article in The American Rifleman in the 30's--written by a man named Curtis who had worked for most of the major gunmakers for about 40 years--some American gunmakers intentionally short-chambered their 2 3/4" marked guns, because they found that slightly longer paper shells in slightly shorter chambers improved patterns. That's because, without the advantage of a plastic wad, one of the problems with deformed shot came when the shot charge exited the shell and came in contact with the barrel. If the case mouth opened slightly into the forcing cone, that offered some protection during the period of initial contact. It's no longer a factor, with plastic wads, but Curtis experimented with a Marlin 90 (starting with a 2 1/2" chamber) and found that the pattern percentage dropped as the chamber was lengthened.

Bell's experiments indicated that lengthening just the forcing cone--not the chamber--often resulted in a pressure reduction of as much as a few hundred psi.

The Brits regularly recommend the use of 67/67.5MM hulls in 2 1/2" chambers. This usually works out fine because the shells are loaded to CIP pressure parameters. However, both Thomas and contemporary writer Charles Fergus reported increased recoil and blown ends on hulls in older guns (I think all pre-1900) with very short and sharply angled cones. Using true 2 1/2" shells solved the problem.

One can always err on the side of caution, but even the SAAMI guidance posted earlier won't keep you totally out of trouble, unless you know how to interpret foreign proofmarks. There are certainly instances in which factory 2 3/4" shells should not be fired in guns with factory 2 3/4" chambers. It's unfortunate that it's not that simple, but unless you're talking strictly US guns and US shells, it's not that simple.

I hesitate to enter into a discussion where physics and engineers tread, but, here I go anyway.

Newton's third law of motion: For every action, there is an equal and opposite reaction.

Years ago I had some contact with the 4.2" mortar and the 106mm recoiless rifle. The 106s were mounted on jeeps. When fired, the projectile left is such a hurry, a vacume was created, sometimes popping headlights and watch crystals. You could watch dust jump off the ground. Yet, the jeep barely moved. Why, as much energy went out the back of the rifle as out the front. The "four deuce", however, has a projectile you can follow with the naked eye for quite a while. I can also remember digging the base plate out of soft ground or firing a couple of rounds to "set" it in the rocky soil of Ft. Hood. That in my book is called recoil.

My point of all this is, the energy of a given projectile, depending on weight and velocity, is going to send exactly the same amount of energy the opposite direction, what I call recoil.

To me, increased pressure can only speed up the projectile, creating more energy, and the same amount of increase in recoil. I think we all pretty much agree, felt recoil can be mitigated by the weight of the gun, recoil pads, and anything else bleeding off the rearward thrust of energy. But, Newton's third law is still there.

As to Joe Wood's Parker tag, I believe all 2 3/4" shells of the period and later were paper and roll crimped. When opened they were 2 5/8".

Don,
I think the pressure/recoil relationship may be something akin to BMEP as it relates to horsepower. Yes, they are independent; you can have low horsepower and high BMEP or visa-versa, but you can't have horsepower totally without BMEP... Increase BMEP and keep all other parameters the same and horsepower increases.

"I hesitate to enter into a discussion where physics and engineers tread, but, here I go anyway."

Read my last Post in this Thread.-Dick

Chuck, I agree that pressure and recoil are tied at the hip, but pressure alone is not a cause or indicator/predictor of recoil. M&M gave a very good anecdotial explaination of recoil vs pressure; he seems perfectly capable of treading along with physics and engineers.

It could be that old, roll crimped paper shells marked 2 3/4" were less than that length when opened. However, looking in my 1940 Shooter's Bible, I find no shortage of 12ga factory loads listed as "2 5/8", which was the 12ga standard until the 1920's or so. Not sure why Parker would specify on a hang tag that 2 3/4" shells are good to go in 2 5/8" chambers when there was plenty of 2 5/8" ammo available.

After reading all the posts referring to the length topic I have concluded that it is perfectly safe to use 67mm and even 70mm shells, loaded to CIP standards in my Manufrance Ideal proved to 1100 Kilos with 65mm chambers.

I had the daring some time ago to post this in the 16ga.com forum and was chastised by a pigheaded, opinionated and extremely impolite member there. I never visited again. As someone said you should not argue with idiots.

Bottom line, as Larry says, it depends on the gun and the load, not necessarily the length of the shell. And of course, if you are not sure better to err on the safe side.

JC

Exactly!



Don, you know me better than that. I never meant to imply it was. Just if you have high pressures vs low pressures, while payload and velocity are a constant, the acceleration curve of the payload and the firearm are different. I'm not saying the crowd that says ejecta weight, velocity = recoil are not wrong, IMO, they are just looking at it from the higher overall perspective. That is: total energy, the E=MC2 level.

I believe the suggestion by Parker and others to USE 2-3/4" shells(all were paper with fiber and paper wads) in 2-5/8" chambers was to maintain a better seal between the shell mouth/chamber wall and wads as they start slightly into the forcing cones. 2-3/4" shells are 2-3/4" long when fired, not 2-5/8".

Several conditions must be understood in this assumption.
First is of course that movement does take place. If, as rocketman stated, the projectile were "Secured" so it could not move the maximum pressure that charge of powder could produce would be generated with no motion of either projectile "OR" gun.
Under ordinary conditions though the projectile will start to move down the bbl & the bbl will start to move in opposite direction in proportion to their weights.
A further condition, velocity of the projectile (along with that of the gun) can be increased in two ways 1; an increase in pressure, 2; an elongation of the time that pressure is applied.
It must be understood that bbl pressure when a projectile is launched is not a constant, but in the form of a curve. When this is understood it becomes quite obvious that "Max Chamber Pressure" is not directly related to the velocity of either the projectile or the gun.
One often sees ads stating that for $XXX a person will perform operation on your gun bbl which will simultaneously give you increased velocity & reduce the recoil. Friends this is total "Unadulterated HogWash". When firing the same identical load from the same gun, with no external modifications, anything which can be done to its internals that reduces recoil, does so at the expense of ballistics, it'd just that simple.
That "Friction" said to be reduced thus allowing exra velocity with reduced pressure was also giving an alternate "Forward Push" on the gun. "IF" a reduction of friction does indeed give you an increase in velocity, it will aslo give a proportionate increase in the rearward velocity (Recoil) of the gun, regardless of any change of pressure.
Again Recoil is directly related to the wt & velocity of the ejecta, Not to Pressure.
The wt of the powder gasses & their increased velocity as the projectile clears the muzzle is also a factor, & the only one not readily calculatable. This can normally be estimated with reasonable accuracy by adding about 25% to wt of powder charge for a shotgun, about 50% for average centefire rifles & about 75% for magnum rifles.
Reports of either "Reduced" or "Brutal" recoil from internal bbl conditions unaccompanied by a through examination giving full ballistic particulars of the firing under identical conditions existing to those while actualy firing from the shoulder, is best regarded as anecdotal & thus disregarded.

Jim, that is what I have always thought, that length stated is that of the FIRED shell.

What should be noted from the Parker label is that they specify the load being used.
The extra length and its eventual slight increase in pressure (as tested by Mr. Bell)
is nothing to write home about and surely in that case improved patterns.

JC

Miller,
That's like saying if the thrust of the Space Shuttle is doubled in one portion of the boost phase and decreased in another to equal the same top speed, altitude and orbit, then the ride to the crew will be the same.

Might we agree that this is prima facie evidence of...uh..."brutal" recoil?
http://www.youtube.com/watch?v=-EVqT3XEzss&feature=related

We are unlikely to ever quantify "perceived recoil" because of the innumerable variables contributing to personal perception ie. how did the subject sleep last night? did he have alcohol? how much? coffee this am? breakfast this am? did he take an ibuprofen for his cervical spondylosis? how's his torn rotator cuff doing? fight with his wife? did he observe the recoil experienced by the previous subject? what did they tell him the recoil was like? what is his previous experience with firearms?

Retrospective and anecdotal studies are always suspect, but with a high enough sample size, they can reach statistical significance. And if Leo Harrison III told me x trap gun had less recoil than y trap gun, to him, I'd believe him.

Doc, amazing stuff on the Youtube page: a speedy six shooter is amazing.

Bottom line, "perceived recoil" depends on the "perceiver", :-)

JC

That is Saeed's, warped sense of humor.

Saeed, a prince of Dubai, owns http://www.accuratereloading.com He is the one who drops to his knees laughing in the video. It is done in his basement reloading room and test range.

What you do not see, is that Saeed is setting up his "victims". He shows them the gun, shoots a couple of very low power hand loads in it. Then he puts in full power loads and turns on the camera.

Here is the load data:
http://www.accuratereloading.com/577tyr.html

It generates approximately 183 ft lbs of recoil.

Pete

I don't think I'd find it funny.

JC

Neither would I, JC. Just explaining it.

Pete

Pete, my comment would have been intended to the prince, never to you. ;-)

JC

Chuck;
My total point is "WE ARE NOT TALKING OF CHANGES OF THIS MAGNITUDE". Give me some firm scientific data as to just how much the acceleration rate is changed by changing a forcing cone from ½" to 1½" for instance, it most certainly will not be cut in half. To have a succesful load we must first stay within max safe pressure & second maintain an adequate pressure to insure complete combustion. Looking at an older Alliant loading guide at a 3de-1 1/8oz load for 1200 fps & using a popular hull, primer & wad, loads were given for three powders. 18grs Red dot, 19½ grs Green Dot & 21 Grs Unique. Now "In Theory" the RD load should reecoil less, because it uses a lighter powder charge, but the Unique load should "Feel" easier because it accelerates slower. Frankly I don't think if I had a box of each & handed them to you randomly where you knew not which was which, you could pick out which was which. Certainly, if that acceleration rate was changed to a significant enough degree, even though the final result (IE MV) was the same the difference could be felt. We are however not speaking of using Bullseye vs Reloader 22 or for that matter even Red Dot vs Blue Dot. RD is not suitable for a high vel 1¼oz load & BD is unsuited for a light 1oz load. As long as powders are maintained within an approriate rate for the load at hand I am reminded of two statements I have read.
1st, was made by Julian Hatcher;
"There are many things which sound real good when said Fast, that won't hold up to a thorough investigation"
2nd, I do not recall where or by whom to give credit;
"98% of advertising is not to sell the product, but to convince a person they have a problem with what they are currently using".
Most of the advertising claiming reduced recoil, without reducing the ballistics, fits both categories.

2-p, very clarifying, thank you.

JC

Miller,
The issue as I understood it was indeed nearly the magnitude om my analogy; a low pressure 5-6 ksi load vs. SAAMI max. I know nothing of pressures from differning forcing cones or backboring nor have any opinion on their effect on recoil. Pattern? Yes, from my direct test experience on forcing cones alone. Backboring? I have no test experience or opinions on its effects.

What I do have the knowledge that when a firearm load accelerates a given payload to a given velocity it does so over a specific time. Change the pressure but keep velocity, payload, firearm weight, etc. the same, and a different acceleration occurs (velocity/time) of the payload. If you believe 'every action has an equal and opposite reaction' you will have to accept that the gun accelerates differently as well.

I believe some of the loads being discussed in comparison, can yield enough difference in this acceleration to be detected by people. They said so. I have no reason not to believe them. I have no data to disprove them. I do have some limited experience of shooting such loads where I believed I noted a difference.

To discount the "anecdotal" experiences of people without data to refute it, itself is to say 'only what I believe is supported by hard evidence, exists' . That approach woulda prevented pretty much any advancements in any field. An open mind to the unproven is what facilitates learning more about it.

Every powder ever made claims to kill farther, give shorter shot strings, pattern better, leave the bore cleaner and produce LESS RECOIL. If there was any truth to any of this BS, we would have come down to only one powder long ago. Trap shooters spend millions every year trying to reduce recoil. While some of them believe some of these unlikely claims, they do not all use the same powder, obviously.
Wad manufacturers make the same outrageous claims. They can't all be telling the truth, can they?
People will still believe what they want, logic and physics be damned.

Chuck, wouldn't the powder's rate of burn be at play here?

JC

JC,
If all the other variables are held constant, that would be the only way I'm aware of to change pressure to such extremes. This is reflected in loading manuals where pressures show extremes while payload and velocity are constant.

Jim,
I think the physics behind what I've stated are pretty solid; "for every action there's an equal and opposite reaction". The differnce in acceleration of the gun has to correlate with a differnce in acceleration of the payload. If exit velocity of the payload remains the same, total energy of the firearm recoil remains the same, I've always agreed on that point. The difference of opinion here is really just about whether a 'mere human' can percieve any difference of loads where pressures go from one extreme to the other while maintaining other factors.

While what you say is all "Theoretically" true I am never-the-less for the most part unconvinced.
In a totally non-related illustration some years back I had a good friend, whom I never new to deliberately "Lie" tell me he got 5 MPG better gas mileage by removing the tailgate from his pickup truck. I have no idea as to how he derived at that figure, but am fully convinced that in his own mind, he believed it. Even though this "Theory" was firmly de-bunked in that the tailgate is running in the "Draft" area of the cab & produces virtually "NO" gas robbing drag, many companies promoted it & made many $$$$ selling mesh tailgates, to those who bought it.
If you go down to your local ammunition emporium & buy a box of 12ga SAAMI 1oz loads it will almost certainly be listed as having a 3¼ DE, giving a nominal 1290 fps MV. Most of these "Low Pressure" 1oz target loads having pressure in the 5-6K psi range will be sub-1200 fps loads. Certainly, they will have less recoil due to reduced ballistics. Another thing to be considered these "LP" loads as given in the loading manuals will have been assembled in new cases. The reloader will most likely be putting them in fired cases. Considering slightly enlarged case volume, possibly weakened crimps, a load that may well be running very close to it's bottom pressure limit for complete & adequatly efficient combustion, may very well fall short of it's stated ballistics. Thus "Until" I see evidence of two loads with X vs Y powders, loaded to "Measured" same ballistics & being fired by a group of experienced shooters under conditions where they can pick the difference without knowledge of which load they are firing, I am simply compelled to treat most statements of "Reduced Recoil" as purely anecdotal.
Incendentally, L Brown has "Quoted" Gough Thomas as "Quoting" a Major British Co (one which "Sold" shells) as running a Blind Test with a large group of shooters with two lots of shells, Slow vs Fast powder, & they "Unamiously" picked those loaded with the "Fast" powder as producing less "Felt" recoil.
"BUT" that would be those having the "Quickest Acceleration" would it not??
I know no particulars as to what actual powders were tested or just what "Extraneous" circumstances may have swayed their "Feelings".
At this point, lacking provable evidence to the contrar, I am still of the opinion that approx 98% of what one will "feel" can be determined by the actual measured recoil produced. This of course assumes all variations fired from the same gun, certainly differences in stocking etc, etc, between different guns can vary the manner in which that recoil is transferred.

Ps; Another thing which should not I think be ignored is the fact of the gun iteslf weighing so much more than the ejecta it is given somewhat of a "Flywheel" effect. While the shot is Accelerating down the bbl at a much varying rate, one feels recoil as one push. It will of course take some amount of variation in the rapidity of this push, to be detactable. Just as different people can have different senso smell, different peripheral vision etc, so can different people have different sensitivity to this "Push". I guess I can just "Count Myself Fortunate" in that if I find with a given gun I can comfortably use 1 1/8oz @ 1200 fps, then I can just randomly use loads that meet that criteria & have absolutely no need to "Sweat the Small Stuff".

We need to go back to first principles to understand recoil!
Newtons 3rd,law [dated 1687] States;" Every force has an equal
and opposite reaction."
Newtons 2nd; law states;"The net force on an object is equal to the mass of the object multiplied by its acceleration."
Simply stated, this means that recoil is equal to: "The mass of the charge[weight of shot+weight of gas+weight of wads] x velocity of charge." This force in turn is absorbed by the weight of the gun in reality the weight of the gun is never sufficient to absorb all of the force generated leaving the shooter to absorb the residual.

As a point of clarification pressure creates the velocity which contributes to recoil.However the equal and opposite force to pressure is the stress rise in the metal of the gun barrel.

I still say you have to sum your forces which is conservation of momentum(assuming elastic collisions with respect to Kinetic energy), Newton's 3rd law though Newton's 1st law is for an isolated system. For conservation of momentum, the gun, powder, bullet, all are at rest; therefore, the initial momentum is Zero; therefore, the final total momentum equals zero - Hence sum your forces and equate to zero. But you can look at your losses, negative forces, like heat mass transfer to the tube, hoop stress as Mr. Hebbes noted and depending on if the diameter of the tube is less than or greater than 20 times(or whatever the definition is) the wall thickness it looks as there could be traveling bulges in forward and rearward directions which leads to barrel harmonics, possibly multi-generation, vibrating, friction because the event is going to be driven to a steady state and the environment is going to do its best to attenuate the progressive event.

Kind Regards,

Raimey
rse

Miller, I believe I sent you--or someone else on this BB who requested it--a copy of the chapter from Thomas' book in which he addresses the above subject. To summarize, the experiment in question--by IMI--involved "nine experienced shots of various build, shooting under a wide variety of conditions with guns of different types, weight and boring. The cartridges were all loaded to give the same velocity to the same shot charge, though by means of powders of various rates of burning. The shooters did not know what they were firing, but were merely required to give marks for recoil. They were unanimous in assigning the lowest recoil to the cartridges loaded with the fastest-burning powder, the dynamical effect of which was checked throughout by electric accelerometers built into the stocks of the guns, and their conclusions have since been widely confirmed."

Since no particular brand of cartridge (nor powder) is mentioned in the text, that would seem to remove any potential "bias" from the experiment. That is, the company trying to prove that THEIR shell (or powder) recoils less than the competition. Besides which, if the company in question makes various types of shells and powders, what advantage is there in promoting one of their own shells (or powders) over another of their own shells or powders?

I did not read the test referred to. I had a book by Thomas, for a while, that seemed to me to be so full of crap that I did not keep it as a reference. I think it was titled Shotgun Facts, even though it didn't contain many, IMO.
However, as quoted, the test above says to me that the faster burning powder produced less true recoil(which was also felt) because there was less of it needed. Right in line with the standard, long accepted formula.
I do remember a similar test in probably Guns and Ammo, some years ago. The conclusion in that test was that the shooters could not detect which shells were loaded with fast burning powder and which contained slow powder. Easy for me to believe, also, as the time difference in the pressure peak betwwen the slowest to the fastest is very tiny.
Still have no idea what Raimey is talking about. No offense, maybe I'm just too iggerant to follow it.

In spite of the fact that a lot of information has been put forth concerning recoil, the original post was:

Answers should be forthcoming.

JC

Not to get into the Do some notice a push more than a whack (the "Get It Over With" G T Thomas school of pain thresholds)?; the pressure biz can be stated two ways. A relatively more inertial load (read more shot) "needs" a relatively slow powder to prevent pressure spiking too high before the load gets moving and to maintain pressure over the time necessary to defeat inertia. The relatively less inertial load (less shot) "needs" the faster igniting powder to avoid outrunning the burn rate over time, increasing the volume which gas must fill, and thereby decreasing pressurization (and efficient burn). The other way of saying the same is that the fast or slow powder needs its appropriate shot charge as a blowout plug in the vessel of reaction. Expanding gas is sure necessary to do the work, transfer energy, or whatever, but where is there shown to be a direct correlation between small-p pressure and velocity in Newtonian mechanics. Others besides Thomas are "hooked on a feeling".

jack

Well, Mark, the answer to your question, "can I shoot 2 3/4" cartridges in a short chamber?" seems to have been answered! First memorize the SAAMI report, then fire your gun remotely while its hanging from a rope, get a degree in physics and mechanical engineering, buy some gauges to test stress, send your loads off to an independent lab to have them evaluated, then fire it from the space shuttle, with the tailgate down, and most important DONT listen to any one who who cant confound you with equations and datums...You are on your own, Pal, I got lost a long time ago...

Larry;
The info I received from you on this was essentially useless. Reason "NO" data was included as to what the test loads themselves consisted of. No mention as to what type of powders were tested. As you have never given any particulars I am asuming you have none. Since Thomas did not state any I also assume either he did not have them, OR didn't want to include them. Now it is a well known & established "Fact", Measurably So, that the progression of shotshells from Black, to Bulk Smokeless, to Dense Smokeless have each resulted in a reduction of Recoil. A 3 Dram charge of BP weighs 82 grains. A 3 Dram "Measure" of bulk Smokeless such as Schultz or DuPont Shotgun weighs 42 grains. A charge of Dense Smokeless equivelent to 3 Drams of BP such as Sporting Ballistite or Infallible weighed 24 grains. These differences in weights are significant enough to make a discernable difference in recoil. Thomas' reasoning on this subject, IE, that the fast powder loads had less felt recoil because It occured so fast the shooter did not have time to think about it, while with the slower powder it was of longer duration so the shooter noticed it more, is about as "Patently Absurd" as saying it's OK to lay your thumb atop the nail head as an aiming point "IF" you "Hit it Fast Enough".
As it stands right now it seems virtually everyone with an opinion on this subject, Except; You, Mr Legg & Myself think one can go to a slower powder & reduce felt recoil. You on the other hand, in your blind devotion to the words of Thomas, without in the words of Mr Bell "Finding Out for Yourself" apparently think one can switch to a faster powder & reduce felt recoil (If you didn't say that, you have said Nothing).
Mr Legg & Myself take the opinion that unless either total weight of ejecta or speed of that ejection takes place no significant change in recoil will be felt.
I Guess everyone will just have to believe whatever they choose to.
To answer the original question;
IF the longer shell were loaded with a load appropriate to the gun & if the loaded shell had clearence past its crimped end in the chamber, I would not concern myself that the end of the fired hull, after the opening of the crimp, lapped up into the cone a bit. I would expect no significant change in either pressure, velocity or recoil. If the length of the loaded shell were enough longer than the chamber that it protruded into the cone before firing, I would refrain from firing it in that gun.

Miller, your last paragraph, I believe, is the best answer and the one that most of us can agree with. Thanks...

LOL!! Too funny. I tested some 2.5" loads with my Lefever yesterday for the first time. After signing my last will and testament, I kissed my wife, petted my dog, tied a string to the trigger, crawled down into my bomb shelter and let er rip. Ok, not really, but shockingly, the twist damascus barrels didn't blow up (Amazing. I guess I'm not the only one to have fired the gun in the last 100 years), they all went bang, some patterned better than others, and some kicked a bit more than others. It was all very scientific, until I got yelled at for using the patterning board when the range was closed. Oops. I thought that was ok, but obviously not.

In all seriousness, one thing that did surprise me was how little difference there was in loads where I used a full plastic wad and ones where I cut the petals off. Pretty negligible difference. That Lefever throws a very tight pattern too, choked m/f. Time to break out the spreader loads, publish my all findings, and send them off to Ithaca.

Miller, I realize that Thomas was a gun writer; therefore, in your opinion, of low credibility--unless he happens to agree with you, which would make him one smart guy. However, he was also an engineer, and I think on this subject, his credentials are at least as good as yours--whatever yours may be.

What Thomas does not state, at least not with total clarity, is whether the shells loaded with the faster burning powder had a lighter powder charge than the ones with slower burning powder. That, of course, would explain why they recoil less. He does specify that the shot charge and velocity were the same, and since he was an engineer--although I don't like to assume--I think it's likely a safe assumption that he realized that a lighter powder charge of faster burning powder, producing the same velocity as a heavier powder charge of slower burning powder, would automatically mean reduced recoil. That puts us back at his conclusion that ALL THINGS BEING EQUAL--same weight of ejecta, including powder, and same velocity--the faster burning powder will reduce recoil.

I don't know if he's right or not. Perhaps time to turn that one over to Mr. Bell as far as measurable recoil goes. Felt recoil . . . well, some people are skeptics when it comes to anything that can't be measured. Except, perhaps, the existence of God.

To return to the original question, I'd say it's highly unlikely that 2 3/4" shells, reloaded to 7,000 psi, would be dangerous in a Lefever chambered at 2 1/2". Pressure might increase slightly, per Bell's experiments. Recoil might also increase if the gun has especially short and sharply tapered forcing cones--in which case one might not want to use the longer shells in that PARTICULAR shorter chambered gun. Or else lengthen the cones.

Hi Larry,
You were doing fine until you got to the forcing cones. Forcing cones have an effect on recoil because________________________?

Just when I thought my latest bout of 'Clarence Darrow Syndrome' (a disease that afflicts many, is often embarassing, but almost never fatal) was over...

Well now that we have the Shuttle and flywheels and measurements of thrust from 2 or 3 grains of powder in the mixed discussion about guns, I'll toss in that I believe acceleration of a firearm in recoil is measureable...you can believe it or not. Accelerometers are common pieces of test equipment which my wife, a vibrations and accoustics test engineer, utilizes in her daily work. So plotting the acceleration curve over time is straight forward stuff.

You can always just lay the gun on a table and pull the trigger with a string and see what if any load makes it jump more.

Chuck, you are absolutely right. This would be the kind of data that could be compared to "felt" recoil by a panel of various size and sensitivity people. Possibly, you would be able to correlate curve characteristics to subjective "feelings." Perhaps you would find some shooters sensitive to recoil acceleration, some to recoil velocity, some to recoil displacement, and some to recoil force. And, there may be other factors.

If we had load by load time-pressure curves, I think we could calculate acceleration, velocity, displacement, and butt plate force. The shoulder contact area over which the recoil force is acting may also be important if we find that recoil pressure against the shoulder is important.

I suspect that G. Thomas's recoil study is accurate. It is unfortunate that he didn't include data so we could check this study. Unfortunately, he wrote for an audiance that generally didn't "peek at the works." Only recently have there been gatherings of "shotgun geeks" to slice and dice everything ever written, sift out the truth, preserve it, and then extend it.

...or stubbornly "disprove it". ;-)

JC

I mentioned in another post, That Diane brought back my "FE" Lefever from Bertrams yesterday. This morning, I shot 50 2 3/4" loads through it on my clays range, broke 48. Then walked up to the east pasture and killed 8 doves with same set up. I admit that without scientific data, that this is valueless. But I still have all my parts, so does the gun. I laid it out on the dining room table, loaded, with a string on the trigger to try the recoil thing but got caught and was forced to stop....

Guns and strings together are usually an indicator of sumpin not so good... or alcohol induced test engineering.

Don,
I think that outfit that makes the pressure trace has a unit that, together with the PT, would yield sufficient data.

Because Burrard and Thomas say so, Jim--Burrard indirectly, Thomas (and others) more directly?

Burrard says: "If the mouth of the cartridge is compressed by being held by the chamber cone, the resistance to the initial movement of the shot charge will be greater and the pressure will be increased." What happens to the increased pressure? If you increase the pressure without changing anything else, won't you also increase velocity--which increases recoil?

Thomas: "Again, the prevalent use of 2 3/4" cases, suitably loaded, for guns with 2 1/2" chambers may be perfectly satisfactory if the guns have normal cones, but not if the cones are exceptionally abrupt, as some are, when the use of the longer case may give rise to objectionable, or at least enhanced, pressures." He refers to a specific case: "This gun shoots the Impax cartridge, with its 2 1/2" case, very satisfactorily. But with cartridges with 2 3/4" cases, though designed for 2 1/2" chambers, it recoils unduly and makes his right arm numb. Three out of four crimps were shot right off . . . " Gun writer Charles Fergus reported precisely the same problem when shooting British shells in longer hulls (but designed for 2 1/2" chambered guns) in a pre-1900 Brit double: Significant increase in recoil, blown ends. No problems with true 2 1/2" cases. And no problems with either shell in a Brit gun from the 1930's, with 2 1/2" chambers but longer forcing cones. The excessive restriction caused by the design of the forcing cone certainly appears to be the culprit. That's why we can't really say that 2 3/4" shells, even if loaded to proper pressures, are a good choice in ALL 2 1/2" guns. If you're getting significantly increased recoil and blowing the ends off shells, you probably ought to stop.

Chuck, we hadnt gotten to the alchohol part yet, but aye the hour draws nigh...I didnt think the string test would hurt anything, it was aimed out the window, at one of the wifes cats...

Now, so far I note, no one has posted any Accelerometer results. I would most certainly love to see such input. I am quite willing to be "Proved" wrong. I will not however simply cave in to "Anecdotal" evidence in which the "Tester" cannot even verify at what velocity his loads left the bbl, other than to say "I took them out of the XXXX FPS block of the loading manual".
As to Thomas yes I understand he was an "Engineer" (So was Casey Jones & he Wrecked the Train) & I am just a low life machinist. Matter of fact "Mr ED" pointed out quite sufficiently my low grade status a while back. I don't however roll over & die quite that easy.
Now as I recall, correct me here if I am wrong Larry, This test which Thomas cited was not carried out at the time of his report. I do seem to recall him stating it was "Formerly" done. Now let me state this as simple as I know how; I have little doubt these tests were carried out & that the results were as stated. I am in no way calling Mr Thomas a liar. What I do find though is that "If" there were data available giving details of the types of powder used etc, & he failed to give full particulars, that was iresponsible reporting. If on the other hand no details were available; for him to publish it & create a cockeyed story as he did to substantiate it as he did was even more irresponsible. To paraphrase him "A shell loaded with fast powder will recoil less because the shooter doesn't have time to feel it". My friend "I Ain't That Thar Igorant Yet".
A few years back when Alliant Powder Co was introducing a new powder to their shotgun line, Select maybe, not sure & not worth hunting up the old manual, They alloted two full pages of their reloaders guide to explainging how this powder would "Reduce Recoil" for the target shooter in comparsion to a typical "Fast Powder". No doubt they were comparing it to their own Red Dot. The burn rate of this new powder fell between Red & Green Dots. The reason, according to them, for this reduced recoil was because it was "Slower", thus a lower pressure peak & slower acceleration. I feel absolutely certain there were people on the Alliant Team equally (or superiorly) qualified as was Thomas, yet their claims were diametrically opposed to those of Thomas. I personally feel that in spite of these folks qualifications, the statements they were making, while technically true, were of such a mi-nute' magnitude as to have no practical effect upon the shooter. They were after all trying to "Sell" a new powder & yes they were "Still" selling their old standby Red Dot. I also "Very Strongly" suspect the test cited by Thomas was performed using one of the older bulk powders in comparsion with a dense powder. No doubt the company promoting the tests was at the time selling shells loaded with both types. No doubt also it was during an era in which the dense powders were proving more economical for the amunition Co's to produce, load & handle etc. No doubt as well there were at the time "Old Die Hards" who desired to cling to the old. It is certainly a possibility this Co was desiring to phase out the bulk type powders, but were afraid of losing customers if they just went Cold Turkey, & that this was a promotion for the dense type of powders.
Now I realize you have already referred to this line of thinking as un-founded ignorance, but I never claimed to be overly smart, but have been made well aware over the years of many "Marketing Ploys".
Bottom line is "If" I were desiring to reduce the recoil generated by my current favorite shotshell powder Alliant Green Dot, I would really not know which way to go. You & Gough would indicate I should switch to Red Dot, but everyone else seems to be of the opinon Unique would be the direction to go. Guess I'll just endure the Green, I kinda like having my teeth Rattled.

This is totally out of context & a misapplication of any thing Burrard said on recoil. If you can prove otherwise cite Chapter & Page Please.

If I were blowing the ends off shells "I WOULD STOP Immediately" irregardless of whether it was accompanied by an increase in recoil or not. A condition causing the ends to be blown from an otherwise sound shell could very likely be a condition which could cause an increase in pressure generated. This might be, but would not automatically be, accompanied by an increase in the velocity. If it did not bring on an increase in velocity it likewise would not bring on increased recoil.

Poor old Thomas takes a licking and keeps on ticking. Very good at spitballing explanations for the results of tests which didn't meet the demands of scientific rigor; I continue to believe that the duration of stimulus shorter than response time argument (somewhere about top of p. 238 in the first Gun Book) remains an ingenious and inviting hypothesis. Human beings aren't capable of being certified as calibrated instrumentation so such tests (however methodically scrupulous) are simply flawed in the premise that they are in any way more than a thought problem. Naturally old Gough would jump ahead and begin to think about the contribution of human neurology. Incidentally, how many distinct arguments can dwell on the head of a thread?

jack

Newton says: "for every action, there is an equal and opposite reaction"

I say: pressure drives the acceleration of the payload. Put that together with father Issac's thoughts above. It (acceleration) is traditionally measured over time, by engineers. If there's some other mysterious driver of the payload, besides pressure in a gun, it escapes me.

The "felt recoil test" by Mr. G.T. had how many samples? That was a statistically significant sample of what population? If you took the same number of people, nah! lets say ...the same subjects, and had them shoot a .22 rifle at a quarter flipped thru the air, how many would hit it on the first shot? How many with a .410? 28g? 20g? 12g? Yet Annie Oakley could do it reliably...and Mr. Furgeson can do it with a bow on occasion. Polls and samples that are not statically significant can and do provide misleading information. Even statically significant polls provide only probabilities of outcomes.

The plot of velocity against time (acceleration) of the payload doesn't look like that of pressure against time (expanderation[?]) of the propellant gases. What's that tell us? Me, very little. You? We're sure lucky the old cork ain't moving two directions like in an IC engine or you guys would have lost me by now. OK, you have.

jack

2-p, I, for one, find you thinking, researech, and writing of great value. Debates, such as this one, do best when all points of view pitch in with all their thinking. The issue we have is lack of currently relevant data. As I said, too bad the former writers didn't give us the data behind their reports.

One would not expect the payload velocity vs time plot to look like the pressure vs time plot. The pressure against the base of the wad is converted to force (pressure times area of the wad base; force pounds per square inch times square inches equals force pounds). Force equals mass time acceleration. The mass is fixed, so the acceleration will vary proportionally with the force. So, the acceleration curve will look like the pressure curve. The gun's free recoil velocity and free recoil displacement will be a mirror image of the payload velocty and payload displacement scaled by the weight difference. However, when the gun is held against a human shoulder, the recoil velocity and recoil displacement are probably going to change, even though the acceleration is not changed.

The above is simple physics. How humans will "feel" it is not so simple. Or, so I believe.

Though not a directly applicable analogy, it reminds me of the little survey George Hickox did with an E-collar, in the seminar I took, to show how little electric stimulation was being used on my dog and the others by him when demonstrating proper E-collar use for training. He passed the collar around and had each of us hold it while he started energizing the collar from the lowest setting up to the point where each person could feel it. I could feel a #1 setting, my wife a #3, others couldn't feel anything until much higher settings up to #12. My dog was responding to stimulation #1 on her neck, other dogs no higher than #3 was needed to get a response. Correction settings were around #10 for the dogs. This collar system went up to #50. He sold a lot of those collars that day. this just illustrates the differences between individuals.

I am not sure this is true. It has long bothered me that there are no internal ballistic programs for shotgun with the ability to predict internal pressures. They certainly exist for rifle and handgun loads. One of the best in that arena is QuickLoad. (Although it does seem to have it's weaknesses.)

I reread Ackley, Powley and Hatcher, whose pioneering work lead to the formula's that are used by today's software.

There is a major impact upon internal pressure when the bullet encounters the rifling. The shape and composition of the bullet directly impacts pressure. To more limited extent seating depth and type of seating of the bullet play a role as well.

QuickLoad maintains a database of powders and bullets. For bullets not in the database you must make detailed measurements and enter them into the software.

The culprit here is friction. As the projectile requires more energy to be driven down the barrel, internal pressures will build.

A shotgun shell is even more complex. That is why most reloaders follow a recipe so "religiously". If you change the wad, you change the friction, which impacts the pressure.

Also, this group is probably more aware of internal pressure issues than most around, because of the age of the guns we are usually talking about. My understanding is that internal pressures in a shotgun peak about 16" from the chamber. So has the maximum velocity of the projectile been reached within the barrel?

Pete

Pete, I would think the highest pressure would be in the chamber, just after the powder ignites, where all the gases are constrained in a small space. As soon as the wad starts moving (and space increasing) pressure should drop rather dramatically.

This is just my logical(?) thinking, ;-)

JC

JC; I do believe you are absolutely & totally corect on this. All I have ever seen correlates this. There have been some pressure curves shown here on the board on several occasions taken from data produced by the Old DuPont powder co back in the early '20's with a variety of powders from fast, slow & Black all loaded to the same nominal ballistics. The point of peak pressure varied by little more than ¼" as I recall & all fell within the chamber of the gun. The reason for establishing the point for recording max pressure in a shotgun's pressure bbl @ 1.0" from breech was that if extended much further it could not be counted on to reliably "always" catch the "Peak" of all loads. The tale told for so many years that Smokeless powders reached their peak pressure some 14" down the bbl in the vicinity of the shooters hand was purely a "Scare" tactic used to discourage the use of damascus bbls. The Gunmakers them selves knew better, with the increased use of smokeless they bagan a gradual "Beefing up" of the guns "Breeches".

Pete, just to illustrate my point: this burst was caused by a mix up in the powders used to reload the shell.
The loader inadvertently used smokeless powder in an amount prescribed for a black powder substitute (could it be called PB?).
There was no obstruction.

This was posted here in 2006 together with the injury the poster suffered on his arm. You'll probably remember.


JC

Thank you Miller. Good for the ego. :-)
Especially coming from you.

JC

JC;
I have no problem at all with recognizing & supporting "Facts" which put down old wives tales. Your reasoning on the max pressure occuring in the chamber was totally logical & supported by facts. One can also recall when Bell reported on blowing up the Parker Damascus @ a pressure of around 30K psi, it blew in the chamber area where it was "Thick", not down the bbl where it was "Thin". Again obivious that max pressure did not carry down the bbl to any extent, as does the illustration you just posted. I do recall this incident being reported here on the BBS.

Diagnosis? 1914 CHE. Unfortunately, no history available

The pressure in a shotgun barrel peaks within the first 1/4 - 3/4 inches. At 16" the pressure will be down in the 1000-1500 psi range and, say, 500-1000 psi at the muzzle. The base of a 12 gauge wad should be about 0.42 square inches. The thrust on the payload near the muzzle, then, would be 210-420 force pounds. Acceleration would be thrust minus drag. The payload will continue to accelerate until thrust equals drag. We know that thrust and drag are getting close as the loss of velocity from shortening a shotgun barrel is small.

If a shotgun barrel is over-pressured, the burst will occur at the first point where the hoop stress exceeds the ultimate strength of the barrel steel. Depending on how the barrel is bored and profiled, this could be anywhere along the entire length. Had the chamber walls been thicker in J-C's example, the burst could still have occured further forward as in revdocdrew's example.

In my opinion Drews example shows all the characteristics of an obstructional burst. This is, however one of the problems with trying to diagnose when no history is available.

Pete,
Currently there is a straingage system available that will plot pressure vs. time. I purchased one a couple yrs ago. Here's a sample plot of five shots overlayed.

ChuckH:

Do you still have the website you posted earlier this year where one could purchase a strain gauge?

I have a non-double question: a hunting buddy fired what looked to be a Winchester 1400 12 bore this past weekend and the first shot resulted in approx. 2 1/2" long thin crack in the top of the frame just right of top dead center(looking from the receiver to the tube) and allowed the barrel to jump forward about 1" showing most of the threads; obstruction? I was busy loading a muzzle-loader and only took a glance as he passed to fetch another gun. I asked if that was the only shot and if he had looked down the tube before shooting. It was his uncle's gun and it had been in storage for about 5 years since his uncle expired. Would a dirt-dobber's nest accomplish such an event?

Kind Regards,

Raimey
rse

Raimey,
Here you go. http://shootingsoftware.com/

That's Paul's '89 Remmy "salesman's cutaway". At least it is now.

jack

To get back to Burrard, Thomas, etc on recoil and pressure:

Miller, I'm not sure that Thomas' theory as to WHY the faster burning powder creates less recoil is correct. However, even you state that you don't think he was a liar, and that the IMI tests to which he refers did happen, and the results were as reported. Did he report "complete" results, including types of powder, etc? Not anywhere I can find. However, if you're going to fault Thomas for that, then you also need to fault your hero Burrard, who only posted the CONCLUSION that long shells (appropriately loaded), when fired in short chambers, do not increase pressure. Thomas, on the other hand, provided an actual chart comparing 10 shots fired in a 2 1/2" chamber and 10 fired in a 2 3/4" chamber, with pressure readings taken at 1" and 6" from the breech, as well as velocity readings. (In this respect, his information is more complete than Bell's, although it only involves one type of shell.)

Burrard did indeed conclude, as I quoted, that excessive constriction of a shell would result in increased pressure. (P. 153, "The Modern Shotgun".) Bell essentially confirmed that in his tests, although in most cases the pressure increase was not very great.

And your recollection of the first "burst" produced in Bell's test is not exactly on target. What happened is that the chamber did indeed peel back where it's thickest, but the source of the weakness was not the solid chamber wall itself. Rather, it peeled back from the hole between the chambers that houses the ejectors. An obvious weak spot, if you stop to think about it.

It amazes me that this discussion continues to come up. I did a test of "perceieved" recoil a couple of years ago by doing a blind test with short and lengthened forcing cones. I had over 300 people shoot my Test gun with identical shells and fill out the questionaire.

I can assure you that you cannot feel minor difference in recoil. You can however, apply your own personal beliefs conciously or unconciously.

I also have a test cradle from my days of testing M14 rifles for accuracy that could be used to test actual recoil I suppose, but any arguments about this subject are of no consequence since no ones mind is going to be changed.

Best, Dick

Larry;
Alliant reloading manual:
Load 1; 12ga 2 3/4" Win AA case, Win 209 primer, Win WAASL Wad, 19gr Red Dot, 1 oz shot, Vel 1255 fps, pressure 10,500 psi.
Load 2; 12ga 2 3/4" Win AA case, Win 209 primer, Win WWAA12F114 wad, 34.5grs Blue dot, 1¼oz shot, Vel 1275 fps, Pressure 9,900 psi.
Now if I am following what you just told me while trying your best to make me look like a total ignorant Fool, load #1 should "Kick Harder" because it has 600 psi more pressure.
Now one more time, Burrard "Did Not Relate" recoil to pressure, he related it to the weight & velocity of the ejecta. "YOU" took what he said out of context & "YOU" said he stated that recoil was increased by that increase in pressure.
Yes the Parker bbl did burst at the weakest popint of the chamber, But the point I was making, As You Well Know, was that it did in fact burst in the chamber & not some distance down the bbl where it was thinner & weaker still. It still showed that the max pressure was located in the chamber area & not 14-16" down the bbl.
As to the test Thomas reported on there is simply not enough detail given to draw a meaningful conclusion, "Period".
Burrard was much more prone to "Over-Detail" than under, to the extent many have stated it is simply too boringly time consuming to read his works. He gave ample evidence that with proper 2½ loads the firing of these loads put up in the 2 3/4" fold crimped case was totally safe & in fact had become the standard practise of the British ammunition makers. What more was needed. Thomas did not recognise this, but rather cited "Other" statements he had made, out of context. Bell stated Burrard totally condemned the use of a 2 3/4" shell in a 2½" chambered gun & that Thomas left much doubt. This can be absolutely verified by reading his article on "Finding out for Myself" whether you want to admit it or not.
I have no idea as to why you have taken it upon yourself to try & disparage everything I say, but there are many others who have expressed appreciation of my posts both publically & by PM. If they are a thorn in your side well so be-it, you best get used to a little prickling, for I intend to stick around.

Just to attest to British ammo makers standard practice here is a page from an Eley catalogue:

2.5"/65mm chambers and 67.5mm cases, oops!

JC

Whatever happened to Dick_dup1 ?

JC

What were the results of your blind test, please? (long vs. short cones)
Thank you,

Miller . . . First of all, paranoia is OK if someone is really "out to get you". I'm not out to get you, and certainly hope you stick around.

Your problem, however, is equivalent to a syndrome well-known in the intelligence business, called "falling in love with your agent". You have this guy who produces wonderful intelligence, you believe everything he says, to the point that you become blind to his shortcomings. Sorry, but comparing Thomas to Burrard on the "long shells in short chambers" issue . . . ALL BURRARD STATED WAS A CONCLUSION THAT IT WAS OK TO USE THEM (if properly loaded). With which I agree. However, Thomas did Burrard one better there, by providing an actual chart of a comparison test--which Burrard never did. That's one case where Burrard most certainly did not provide an excess of detail.

Both Burrard and Thomas needed better editors. What sometimes happens, with individuals recognized as "experts in their field", is that the people doing the editing feel unqualified to make any changes whatsoever. Both Burrard and Thomas, if taken out of context, can be interpreted as saying that you should not use long shells in short chambers, even though both of them reached exactly the opposite conclusion. I do agree with you that Bell is guilty of quoting both of them out of context. I have absolutely no problem "admitting" that. Unlike you and Burrard, I have not fallen in love with either Bell or Thomas to the degree that I cannot see shortcomings in their writing.

If you want to quote me, Miller, you might want to use the quote function--because your "recollections" are often erroneous. I did not say that Burrard related pressure to recoil. What I said was that his statement about an extreme constriction of a case mouth causing a significant increase in pressure can be read as an indirect indication that recoil will increase. I think you'll find that if there is sufficient constriction that you're blowing the mouths off the ends of hulls, that will indeed result in an increase in recoil. Or at least that's what both Thomas and Fergus say. Were Burrard around to comment, I doubt he'd question it either, because he was certainly aware of the problems due to excessive constriction of the case mouth by the forcing cone, since he made those comments in writing.

Sometimes foot in mouth gets the better of me. I have had this for several years and should have known better....



Pete

Well Larry We have beaten this around about enough with nothing accomplished. For the most part on this last post I will simply say "Take a good Long Look in a Mirror"
But let's just get right down to the very Gist of the matter. You have as of yet failed to state even one reason, obivious or otherwise, "WHY" a gun using fast powder would recoil less than one using a slow powder, given equal ballistics "Other Than" a
I do quote Burrard from time to time, because as you have so well pointed out I am not an "Engineer" I am not an "Authority Figure". I have never though, to the best of my recollection asked anyone to buy anything, "JUST" because Burrard said it. I have to the best of my ability tried to include a "Reason" as to "Why" he said it.
I am still begging for one single reason "Why" I should acept the cited "Test" re Fast powder other than "Thomas Said It".

Pete, do not punish yourself.

"Errare humanum est", said the duck getting off the hen.

JC

What amazes me that folks still think 65mm means low pressure or low recoil. It's not always true.

Note the above posted pressure curves. Note these would not in reality start at 0" as the shell would have a base wad, but note how high the pressure rises before hardly any movement of the charge itself takes place. Also note this initial movement of the charge is a very critical factor. Too soon & pressure will not rise quick enough to insure adequate combustion & a "Squib" may be the result. Too late & pressure can Spike to a dangerous level. Way too late as in putting a stiff charge of a fast powder behind a heavy shot wt & the charge might not leave the bbl at all. In this case the shooter would experience hardly any recoil at all, but most likely would note the "Blinding Flash" as the chamber top lifted off in front of his face. (Very High Pressure)
The question boils down to exactly how "All" factors interact to affect the acceleration of the charge down the bbl, & exactly how that acceleration affects what the shooter feels. I am very willing to recognise that "IF" that rate of acceleration of the gun can be showed to vary to a significant degree, that even though total recoil developed remains the same, there can be a difference in how it is absorbed by the shooter. In this case I Would be in the camp who believed the "Slower" rate of acceleration would be the most comfortable to fire.
I am at still however, this point thoroughly convinced that within the parameters of currently available shotshell powders suitable for consistent reliability for a given load that not enough variation will exist for a shooter to seperate two loads into "Mild" vs "Brutal" by the firing of a few shots. Possibly there might be a slight difference in "Accumalated" fatigue by the firing of a large number of shots over a relatively short time. In this case extreme care will have to be excerised to insure one is actually testing the different loads & not "Themselves" over different sessions as alluded to by another poster, several pages back.
This is esentially my stand on this & I am "Always" open to any "Meaningful Input".

Everyone has given their opinion and some have given a lot of research and great information. The whole thing still comes down to that no one has answered his original question. So Mark I will give you mine. Your gun has 2 1/2" chambers and you are reloading low pressure-low velocity loads in 2 1/2". I would say that 7,000 psi loads and up to 1100 fps would be fine.
I don't know why with all the available shell sizes out there now and the low pressure-low velocity selection why anyone would want to shoot shells that were not made for their gun. Years ago ingnorace was bliss, but not today with all the information out there.

In gettng back to Sherman Bells article on "Finding Out For Myself" I believe he fired one proof round in each barrel and that was it. Since no one knows what modern shells actually produce in shorter chambers and you will be firing more than one why take a chance.
Just my opinion.

Miller,
Isacc Newton's 300 yr old laws of motion address your uncertainty about acceleration of the gun vs. the payload. They basically say: if you push harder, the object accelerates harder, and; if there is a force it has an equal and opposite reaction. Pressure is the origin of the force as it pertains to guns. Put all this together and you can see why I conclude that the gun accelerates differently with different pressures.

What a person can 'feel' or what fatigues a particular person more than another is very subjective. So if a person says a particular load is less comfortable to them than another, what basis would I have to discount his 'feeling'?

Hard to argue with that.

David,
I believe Bell did fire more than one shell for each test, I just don't recall how many. He did indeed find somewhere between 0 and up to about 15% increase in pressure on the testing he did. I've fired a number of shells in an instrumented short chamber but not in comparison to a 2 3/4" chamber. The pressures were what I found to be acceptable (6500 psi) for my use.

That would be because larry can’t give you any facts or reasons. He blindly quotes Thomas and gets defensive whenever anyone questions him. for him to accuse someone else of unflinching devotion to a writer is the apogee of conceit. I adhere very closely to what Burrard wrote because it all holds up under scrutiny and everything adds up.

I don’t doubt Thomas performed some test and I don’t doubt he achieved the results he claimed. The problem is without documentation they’re trash. Here’s the problem: step one of the scientific process is “formulate an hypothesis”. Every subsequent step is specifically designed to prove said hypothesis. I’ve spent enough decades in a research world to have seen what people do when data doesn’t match their pre-conceived notions: they come up with a reason to discount that data. Gough Thomas performed some test which proved his preconceived notion was right because the test was arranged to accomplish that end.

Any idiot can stand up and say “tests have shown blahblah ….” unless a comment like that is accompanied by documentation of every particular, every facet, and preferably the raw data as well, of the test, any conclusions drawn are plain and simply garbage.

Don’t believe it? try selling a $75 million fighter to USGOV and saying “tests have shown it meets your criteria. Trust us.” I guarantee you they won’t. they will want back up.

Roger

Chuck;
I am indeed following what you are saying. However, think very seriously about this question before replying.
Again looking an an old Alliant guide, I find two loads both with 1 1/8oz shot at a listed 1200fps. All components are "Identical" Except the wad. one used a Rem Fig 8 @ 10,700 psi, the other a Rem RXP12 @ 9,800psi. Now again think this over "Real CarefuL", can you "Positively" state the load using the Fig 8 accelerated faster, because it showed the highest pressure. "OR"?? did the Fig 8 wad take a tighter hold on the walls of that particular brand of case for whatever reason & Actually "Retard" the acceleration, creating the higher pressure. Remember "All" factors have to enter the equation. I certainly do not find it true that acceleration can be figured from the max pressure recorded in a pressure gun, nor for that matter, even from the entire pressure curve. Certainly a factor, But "Not" the only one.
I also think since the majority of plastic wads are rather loose in a bore & depend upon obturation for a seal, if not given a quick enough blow to ensure obturation, might quite well move down the bore with faster acceleration than if a faster powder was used giving that tight obturation, resulting in greater friction & keeping the pressure up but retarding movement. Many Many factors to be considered. I really think the only true answer lies with an accurate Accelerometer test of the gun's movement itself, while firing different loads.
Actually having followed your posts here for some time, I must say I am quite surprised you have seemingly failed to consider any factor other than just the pressure. This does not seem compatable to your usual thouroughness of a subject.

Miller, do you often look in the mirror and argue . . . with yourself? Why should I have to give you any reason why a faster-burning powder seems to recoil less, when:
a. You agree the IMI tests were carried out;
b. You agree the results were as stated (the shooters unanimously observed less recoil with the faster powder); and
c. You're stating that Thomas did not lie about the tests.

Your only complaint--which is quite accurate, I readily admit--is that Thomas did not print complete results including powder types involved, etc. True--just like Burrard did not publish complete results for his conclusion that long shells, loaded to proper pressure parameters, are perfectly safe in short chambers. And in that latter case, Thomas did in fact publish complete, comparative results.

Looks to me like a tie between two dead Brits.

2-p and LB, thorns and barbs aside, you two have done a commendable job of debating the issue from the Thomas-Burrard points of view. Thanks.

2-p, the acceleration will follow the wad base force, as generated by the pressure, minus friction drag. The amount of friction drag will be a function of sliding coefficient of friction between the plastic wad's obturation section and the hull wall followed by the steel barrel (think pretty low) and the wad's velocity. 10,000 psi is going to exert about 4200 force pounds on the wad base (0.42 square inches). Suppose that about 0.2" of the wad skirt is in contact with the hull wall/barrel and has a cirumference of 2.3" for a contact area of 0.46 square inches. So, the coefficient of friction would have to be 0.91 (0.42/0.46) to stop acceleration. Another way to look at this issue would be the possibility of the wad holding the force on its base with friction. Suppose the thickness of the wad skirt is 0.050" and has a circumference of 2.3". The area available to resist the 4200 lbf load is 0.115 square inches. 4200 lbf over 0.115 sq in requires a tensile strength of 36,500 psi. Both the case of a friction coefficient of 0.91 and a tensil strength of 36,500 psi are implausible. Somebody please check these numbers. Unless I calculate wrong, the acceleration is going to follow the pressure curve pretty close for the first part of the shot.

Rocketman:

The coefficient for clean steel should be around 0.6-0.8 but I'm not sure of the value for plastic on steel(plexiglas on steel is about 0.5 and plexiglas on plexiglas is near 0.8). Would the forcing cone surface have a higher coefficient of friction? Also, I don't see it but did you include the weight of the load along with the wad in your friction force(Normal)?

Kind Regards,

Raimey
rse

Rocketman:
Very good post & sure throws some Meat into the discussion. One question, in your opinion what does cause the 900 psi pressure rise of the Fig 8 over the RXP12. That is about an 9.2% increase. Certainly the difference in the wts of the two wads would not account for a 9.2% increase in total ejecta wt.

I found some published coefficients for teflon on steel. They showed .04 for dry condition. Polyethylene HDPE is what I believe is most of the wads are today. It's pretty slippery stuff and self releases from molds, which is why it's so popular for so many products. Tensile runs around 15 ksi. Some of the really tough steel type wads are nylon or other and can be very high tensile strength. Kinda gives a swag, but Miller's right; only an appropriate test would give the answer to any degree of accuracy.

But the notion that acceleration of the payload would not roughly pace with pressure due to differences in wad friction, when comparing significantly different pressures in loads otherwise the same, has little supporting it.

These are quick and simple calculations. I didn't include weight as I don't think it factors into this part of the problem. I wasn't trying for total friction force, only the numbers if the wad generated sufficient friction to block movement; one very special case. Forcing cone friction should closely follow the barrel bore. Chuck gave us some real numbers for plastics closely related to wad materials. Also, the wad will quickly heat from the friction and powder gas. My guess is that friction will go way down due to surface lubricity as the wad heats.

2-p, my guess would be that the exact shape of the initial combustion chamber would be important and the exact fit of the wad against the hull wall. If the wad had a somewhat loose fit, there could be a bit of initial blow-by. If the wad had a very tight force fit to the hull wall, there could be some initial resistance to movement above the wad-shot weight. We know that peak chamber pressure is pretty sensitive, so these factors seem plausible to me.

Chuck, thanks for the Mu values. I'd guess the HDPE is close to teflon in Mu. And, I surely agree that we need some accelerometer or high respones load cell force data!!

Fluid friction coefficients as well as all other friction coeffs can't be derived or calculated and are empirical in nature so a guess would be a start but would have to be validated. Since we are dealing with a fluid event, there are going to be forces tangent to the wad surface as well as perpendicular. What would the coeff. of friction be for teflon on teflon and would the event realize peak pressure during the teflon-teflon friction?

Kind Regards,

Raimey
rse

I think wads and hulls are close relatives of HDPE - pretty slick stuff. The peak pressure usually occurs within 1/4" to 3/4" of displacement, so the wad is still generally within the hull.

If the wad is still in the hull, then the length of the shell would make no real difference.

Pete

I agree that the differences should be relatively small - say as found by Bell. I imagine that the hull mouth opening into the cone does add a small amount of resistance to wad movement, just enough to bump peak pressure a few %. Burning pressure is a big factor in nitro powder burn rate. As a consequence, nitro powder gets increasingly touchy as pressure goes up. Pressure too low and it doesn't burn well. Pressure too high and it becomes intolerant of small variations in burn factors.

I've seen one opinion that smokeless needed to achieve a pressure around 7k to perform; is that close, fact or fiction or does if vary from powder to powder? Are most shotshell powders flake?

Kind Regards,

Raimey
rse

Raimey,
Based on the results stated here by some of the low pressure loaders that use very slow powders, I'd say it's likely the low end pressure/efficiency issue is dependant upon the burn rate of the powder. I've been using a bit faster powder than some others but loading to similar pressures and velocities and have noted relatively good powder burn, albeit not as clean as a higher pressure load using this powder (Hodgden Clays).

ChuckH:

Thanks for the info. Regarding posted pressure, for every cartridge a manufacture makes do they fire the cartridge in a test gun to get the pressure or it is a calculation. group velocity outside the barrel isn't that difficult to measure but I was curious about their pressure values like you would find here:
http://www.tiropratico.com/ricarica/manuali/REX%20Nitrokemia-.pdf
Is all the given data from measurements?

Kind Regards,

Raimey
rse

Here is the procedure for testing ammunition http://www.hpwhite.com/101-00.pdf

Based on ANSI/SAAMI Z299.2-1992 which basically says for 12ga,

Maximum average pressure: 11,500 psi
Maximum probable lot mean: 12,100 psi (a calculated figure)
Maximum probable sample mean: 13,000 psi (a calculated figure)
Proof loads (AKA Blue Pills) are 19,000 to 20,500 PSI

A selected number of shells from each production run are tested to provide a satistically meaningful result. To not do this is inviting litigation. There are many examples of ammunition makers issuing a recall.

The procedure for testing firearms is here http://www.hpwhite.com/100-00.pdf

If you want the complete ANSI/SAAMI specification it is for sale here: http://www.saami.org/Publications.cfm

Pete

The local CIP proof house does actual tests on batches of locally produced and imported shells. They say the local production is more consistent than some imported brands.

JC

Re hull length in shorter chambers and resulting pressure increases . . . In one case, Bell got a pressure increase of almost 1,500 psi. But that resulted from a 3" shell being fired in a 2 1/2" chamber. I'd guess that those instances in which extreme constriction takes place, apparently due to very short forcing cones and hulls that are too long--resulting in ends blown off the shells and wicked recoil--there might be similar pressure increases.

My recollection of his article is that the only shells that blew off part of the crimp end were extreme mismatches. 3-1/4 or 3-1/2" shells in 2-1/2" chambers. I don't think he even mentioned recoil. He maybe did not shoot the shells from his shoulder, either. I don't have that magazine anymore. Assuming that the small increase in pressure that MIGHT occur when firing a 2-3/4" shell in a 2-1/2" chamber, because the extra length ends half-way up a 1/2" long forcing cone MIGHT cause an increase in velocity and would therefore cause an increase in recoil is as silly as the long forcing cone salesmen claiming the longer cones cause NO loss in velocity but magically reduce recoil. Ditto the same claim illogical for backboring. BS.

Jim,
I think you're right about not shooting it from the shoulder. I believe it was a laboratory bench mounted pressure gun.

One unknowable variable in this entire equation that no one brings up is an individual gun's history. I hasten to think that a 100 yr. old gun has likely had any number of various rounds fired through it during its lifetime, from low pressure loads to magnums. If it hasn't failed by now, I doubt that shooting a slightly longer low pressure shell is going to all of a sudden make much of a difference. It may sound like I'm answering my own original question regarding this post, and perhaps I am.

Having said all that, and having read these fifteen pages of posts, it's still probably better to be safe than sorry. Why tempt fate?

Put another way, be reasonable, careful until someone defines what is safe. Everything we do involves risk.

Not quite that much of a mismatch, Jim. "As with the previous magnum load, the 3" hulls that emerged from the 2 1/2" chamber looked terrible. Several had portions of the star crimp area torn off. All had ragged cone-shaped mouths." And no, they were not fired from the shoulder. "I was glad we had the use of the strong test receiver and barrel for this stunt. You would have to be a complete idiot to do this to a real lightweight game gun."

Jim, if you don't believe that an increase of 1500 psi and blown ends on shells might also result in an increase in recoil, why don't you try it for yourself and see? Sort of in Bell's "Finding Out For Myself" mode. Personally, I am more than willing to accept the reports from Thomas and Fergus that long shells fired in short chambers with short cones produced similar visible results to the ends of the shells; so why is it unlikely that they also produced similar increases in pressure? And in both cases, they reported significantly increased recoil. And in Fergus' case, he fired the same long shells in another gun, also with short chambers but with longer forcing cones, with totally different results: no blown ends on the hulls, no noticeable increase in recoil. He also reported that true 2 1/2" hulls worked fine in the gun with the short cones.

Generally speaking, as Burrard, Thomas and Bell all agree, I don't think a 2 3/4" hull loaded to appropriate low pressure will result in anything other than a slight and inconsequential increase in pressure when fired in a gun with 2 1/2" chambers. I do it all the time with my own 2 1/2" guns. However, I have heard enough "exceptions to the rule" to accept that there are indeed exceptions to the rule, and that the exception appears to be the result of guns that not only have short chambers but also very short forcing cones.

Can you post the muzzle velocities of any of these cited circumstances?? Did Fergus report the MV's of the shells fired in guns having different cones?? If the increased pressure resulted in an increase to the MV of the load, then there is an obvious reason for an increase in recoil. IF on the other hand the increased pressure was a result of a retardation of the opening of the crimp &/or the movenment of the charge & no increase in MV occured, then no increase in recoil occured. If, with no other data, we accept that he reliably reported an increase in recoil, then we "Must" of necessity asume the end ballistics of the load were also altered. I have no problem accepting this. If, however you are promoting that this rise of pressure, increased the recoil without an acompaning increse in the discharge velocity of the charge, then I have an "Extremely Great" problem in it's acceptance.
Pressure moves both the charge & the gun. Resistance to movement results in an increase in pressure. When only weight of either gun or charge is entered into the equation the movement is directly proportional to those weights. Any other factor I am aware of which can be entered into the equation which give a resistence to movement applies equally to both gun & charge. Thus no change of the movement of one can occur without an equal change of the movement of the other.
The only part of this entire diatribe still even really open to debate is just how much change in the rate of acceration of that movement is required for an average shooter to detect it. This I feel will remain un-answered until we have some very reliable accelerometer data coupled with "Extensive" input from a large number of "Unprejudiced" shooters, done under conditions which prevent "Preconceived" ideas affecting that input.
Less there be any misunderstanding due to various statements attributed to Burrard, I will state I have had the "American" edition of his works which combined the three volumes & appendixes into two books for some 40+ years. I have over these 40+ years referenced them extensively. "IF" Burrard ever attributed any factor to recoil other than; Wt of total charge (IE shot, wads & powder), Discharge velocity of that charge, VS weight of the Gun I would love to "Re-Read" it as I have totally forgotten it. Volume; Chapter & Page "PLEASE".

"Jim, if you don't believe that an increase of 1500 psi and blown ends on shells might also result in an increase in recoil, why don't you try it for yourself and see? Sort of in Bell's "Finding Out For Myself" mode. Personally, I am more than willing to accept the reports from Thomas and Fergus that long shells fired in short chambers with short cones produced similar visible results to the ends of the shells; so why is it unlikely that they also produced similar increases in pressure? And in both cases, they reported significantly increased recoil. And in Fergus' case, he fired the same long shells in another gun, also with short chambers but with longer forcing cones, with totally different results: no blown ends on the hulls, no noticeable increase in recoil. He also reported that true 2 1/2" hulls worked fine in the gun with the short cones."

An increase in pressure of 1500 psi MIGHT increase velocity and therefore increase recoil. BUT, the increase in recoil WILL be because of the increased velocity, NOT because of the increase in pressure.
And NO, I don't believe blowing the ends off of shells will increase recoil.
I'm amazed at the lengths you pressure believers will go to prove that pressure CAUSES recoil. It does not! rates of accelleration and all the other smokescreens offered are just smokescreens. Recoil is caused by the gun's reaction to the velocity of the ejecta, period. Learn to live with it. Facts are facts. Physics is physics. BS and speculation are just BS and speculation.
You might as well say the primer causes recoil because without it, there would be no burning of powder and expanding gases to cause the velocity of the ejecta. Or maybe it's the trigger's fault.

I think your average 6lb shotgun firing 1 oz. loads at 1200fps recoils at a velocity a bit over 12 fps. I didn't even have to take off my shoes for that one! Probably should put one on rails and time it.

jack

Miller, I can't tell you where to look in your copy of Burrard. I have only an extract, and he addresses the effects of compressing the hull in the cone about 5 paragraphs into his discussion entitled "Length of Cartridge": "If the mouth of the cartridge is compressed by being held in the chamber cone, the resistance to the initial movement of the shot charge will be greater and the pressure will be increased." Well, we know from the Bell test (cited earlier) that there was a significant increase in pressure when a hull extended well into a forcing cone. If that "squeezing" effect initially retards the acceleration, with the greater pressure building behind it, does it not make sense that the acceleration--once the "obstacle" (case mouth) is removed--will be greater? And could that not explain an accompanying increase in recoil?

You are correct in stating that neither Burrard nor Thomas nor Fergus give velocity figures. However, both Thomas and Fergus report the same visual evidence (blown case mouths) that Bell reported, when he also reported a significant pressure jump. Or are you doubting three separate reports of blown ends on cases? And if, in the case of Thomas and Fergus, they report the same visual evidence, why is it not possible that they also experienced significant increases in recoil? Just because they didn't measure velocity does not mean that it did not increase. Or, the increased recoil may have been due to the change in acceleration when the charge was finally released, with greater accompanying pressure.

Fergus describes his experience with British shells "approved for use in 2 1/2" guns" in a pre-1900 Westley Richards and in a Jeffery (also 2 1/2") from the 1930's. (The Westley, by the way, was stamped as having passed reproof some time after 1954.) In the former, blown end and "stiff recoil that caused me to stop and examime the discharged cartridge". Yet the gun performed fine with true 2 1/2" hulls.

Thomas is well aware of the same situation and comes to the same conclusion: On some guns with "exceptionally abrupt" cones, "the use of the longer case may give rise to objectionable, or at least enhanced, pressures." Same thing Burrard says, using very slightly different words--Burrard referring to the compression of the case mouth. (But how else is that going to happen, except in the forcing cone???) Thomas also verifies that the gun in question works fine with true 2 1/2" shells, whereas "with 2 3/4" cases, though designed for 2 1/2" chambers, it recoils unduly and makes his arm numb." And the crimps are blown off.

We already know that the pressure increase is real. All the authorities agree, and Bell's tests prove it--significantly so, when the case extends well into the forcing cone. We also know that the blown ends are real: Bell, Thomas and Fergus all report the same evidence. Bell was using a pressure gun, so he couldn't comment on recoil. Nor did he report velocity, other than to say--for all the tests he conducted--that "velocity of all loads remained essentially the same", without additional specifics. (I would've liked to see the velocity on that 3"er with the blown ends and the big pressure spike.) So perhaps the difference in acceleration resulted in the increased recoil--which, given that the other two pieces of evidence (pressure increase and blown ends) are measurable or observable, I believe really did increase. Why doubt the third effect when we know for certain that the other two happened, and they're being reported by the same people?

But hey, if you guys want, go ahead and continue telling people that any 2 3/4" hull loaded to the appropriate pressure will work just fine in any gun with a 2 1/2" chamber, regardless of differences in cone length and angle. For that matter, while you're at it, tell them to disregard it when they blow the ends off the hulls. And if they feel increased recoil . . . well, it's all in their heads.

Larry;
I have definately not made any such atatements as that & "YOU" JOLLY WELL KNOW IT!!!
I in fact made the statement "IF" I fired a shell in a gun & the result was torn case mouths I "WOULD STOP IMMEDIATELY" & it did not matter "IF" it had excessive recoil "OR NOT". I have also on several occasions even stated I would not fire shells whose loaded length extended into the cone. I have been generally Fru-Fraued for this, but have stood by it. Neither Thomas or Bell to my knowledge addressed this situation, but Burrard did. Also note I "Have Never" advised anyone to ignore an increased recoil.
Now here is a quote you made back on page 9.

Note by the word "AND", as well as You put the excessive recoil "First", this would be quite easy to interpret that one could ignore the torn case "If" they did not get excessive recoil. This is simply not the case & I will continue to warn people that it is indeed possible for conditions to exist which can create an excessive max chamber pressure without increasing the velocity & recoil of the gun. Your continuos use of the terms Stiff, Vicious, Excessive, Brutal etc can quite easily leave the impression on a reader that if they put a load in their gun & fire it & don't "Get their Teeth Kicked Out" they can go merrily on their way & have no fear for themselves or their gun. Now Larry you are a noted Gun Writer & held in high esteem by many (Myself included in all I have read of yours "Other than Ballistics"). You need to be extremely careful here as you can quite easily lead someone into trouble by seemingly indicating it is inevitable that an increase in max pressure "Will Always" result in an increased recoil. An increase in velocity & recoil will indicate an increase of the total average pressure under the curve, but this is altogether different than max pressure. Max chamber pressure is not a "Direct Indicator" of either Velocity or Recoil. While this is strictly speaking a shotgun board, these principals apply equally to Pistol, Revolver & Rifle. Many guns have been Wrecked over the years without the shooter ever feeling an excess recoil.

Good catch, Miller. I should have said "If you're getting significantly increased recoil and/or blowing the ends off shells . . . " Goes to show you that all of us can use help from sharp readers (or editors who understand the subject).

That being said, I don't think the issue addressed by Fergus and Thomas has anything to do with the loaded length of the shell extending into the cone. Unfortunately, the only unfired Brit shells I have at present are true 2 1/2". However, I have a fired 67MM Game Bore 16ga, and it is exactly the same length as a fired Remington 16ga Game Load. Both crimped, so it seems to me their unfired length would also have to be the same. And while I agree with you that an unfired shell extending into the cone should be avoided (that's almost certainly what happened when Bell touched off a 3" shell in a 2 1/2" chamber), the only way that could be the issue in the cases reported by Fergus and Thomas is if the guns in question (in which the ends were blown and sharper recoil reported) had chambers shorter than 2 1/2". We know that the 67MM shells, which the Brits say right on the shell boxes are approved for use in guns with 2 1/2" chambers, do in fact function just fine in MOST guns with 2 1/2" chambers. So my strong inclination is to agree with Thomas and Fergus that the culprit is the length and taper of the forcing cone, not the length of the chamber--although it would be interesting to measure the chambers on those guns in which problems have been reported, then do the same with other 2 1/2" guns that handle the same shells with no problems.

I suppose it could be that Brit gunmakers prior to 1900--like some of their American counterparts a few decades later--were intentionally short-chambering their "2 1/2" guns, and for the same reason: in order to get improved patterns. That'd work fine as long as the shells were true 2 1/2", but might indeed result in the unfired shell extending into the cone if the chamber were somewhat shorter than 2 1/2". Haven't ever read anything indicating the Brits adopted that practice, but since some American gunmakers did, I guess you never know.

Miller, Jim and Larry, Chuck, and others,
All of you bring up great points and a lot of your knowledge about this subject. For me it is a little too deep. I reload low pressure, low velocity shells in 2 1/2" and 2 3/4" for some old L.C. Smiths I have. Mostly because I have the time to do it and because of the loads I want. None were ever tested by me, but all the loads were from either tests done by Tom Armburst for the 16 ga Reloaders Group or form reloading guides.
I don't shoot 2 3/4" shells in 2 1/2" chambered guns, why, because I don't feel it is safe. I'm positively sure that previous owners of the 20 ga "elsies" and 16 ga "elsies" I have had 2 3/4" shells through them, why, because ignorance is bliss. Most people that buy older guns have no idea what the chamber length is and just shoot todays modern loads designed for heavier payloads. This is why a lot of the L.C. Smiths we see have cracks behind the sideplates. This was especially true from the 50's-80's when we didn't have the selection of shells we have now. Shells then were loaded Magnum or Maz loads and people just used them, and I'm sure they noticed the recoil.

I believe Jagermeister stated a good statement, people think 2 1/2" shells mean low pressure-low velocity, why would it, it's just a shorter shell.

Also firing a 3" shell in a 2 1/2" chamber, idiotic for one and even though it was a test and nothing happened, you can't tell me recoil wasn't greater. First of all the 3" shell had more powder and more payload of shot than a 2 1/2" shell.

JayCee, your picture of the blown barrel, I don't reload black powder but the difference between the two powders is probably 3-1, so he used approximately 100 grains of smokeless, talk about excess, he's lucky.

AH Fox HE Becker bored 2 3/4" chambers, after abundant 3" magnum loads. Courtesy of David Trevallion.





Suspect the recoil was a tad...uh...brisk

Besides the gun flying open, and after messing his pants I wonder if that had anything to to with.......pressure?

When most of us speak of pressure, we're speaking of the "spike" and the peak pressure produced. Peak pressure certainly has very little correlation with ballistics or recoil. Pipes mentions pressure "under the curve". I'd think you could average the plot for sustained pressure over time and that psi number would be the same for all powders and powder charges producing the same ballistics for a given payload. I continue to think that the time to "peak" is bound by necessity to the inertia of the payload.

jack

Hello David,

The owner of the blown barrel I posted was really lucky in that he "only" has an ugly scar on his arm to show for it.



You in the US are somewhat cursed with SAAMI standards, but modern loads do include CIP standard loaded shells that have reasonable pressures of 2 3/4" shells you can use in 2,5" chambers.

The fact that plastic shells are used should also be brought into the equation: the difference in thickness of a paper hull going into the forcing cone is not the same as a plastic one doing the same. JMTC

JC

Larry;
I think we are actually making progress. I think you have made an accurate assesment of the situation Fergus encountered. As I recall his acount the gun was a very early one & the cone was so short as to be almost a step.
It is also noted that 65mm & 2½" are not mathamaticaly identical. 2½ = 63.5mm. I have not had opportunity to measure a large number of British guns but from what I read I believe that many, if not most nominal 2½" British guns did have the 65mm chambers which are about 2 9/16". Now if this early chamber were a true 2½" (It is my understanding some were) & if that cone was on the order of just a 30°-45° chamfer at the end, then even a 67.5mm hull could have entered the bore proper, not just a portion of the cone. I highly suspect this was somewhat the condition Fergus encountered. This could indeed create a check to the early movement of the shot causing a rapid build of pressure. I can also see a sudden release taking place which would cause this high pressure to give an enhanced velocity to the charge & in fact the cutting off of the portion of the hull in the bore may have provided this release. This enhanced velocity would then create the extra recoil. It is though quite possible that with a different set of conditions A pressure spike can occur but this sudden release not happen & there be no increase in either velocity or recoil. So yes Larry, any abnormal increase in recoil should most definitely be immediately & thoroughly investigated for cause, But the point I have been trying to instil is "If" it does not occur, one cannot automatically determine no abnormal pressure has occured. To load a longer shell in a shorter chamber established guidelines must be adhered to & Recoil is not a reliable indicator of Maximum Peak Pressure.

Good points, Miller--and from what Fergus wrote, I think the situation he encountered was as you describe it.

I don't have a recent Brit 2 1/2" gun to measure. Most, of course, are now chambered 2 3/4"/70mm. The older 2 1/2" guns reproofed recently are remarked, I think, 65mm--even though I do not believe any actual modification in length has been made. So even though 2 1/2" does not equal 65mm, I think the Brits treat the two as being the same. I found it interesting that Fergus' old gun passed reproof some time after 1954. Apparently the proof loads didn't produce anything unusual, even though the 67mm shells did.

I think a reasonable conclusion is this: mouth of the unfired hull extending into the bore itself, or into a very short and sharp forcing cone, may very well produce dangerous results in terms of a pressure spike, visible damage to the hull, and perhaps increased recoil.

David;
As I recall this occurance the owner of the Remington dbl mistakenly used smokeless IMR PB powder & loaded by black powder volume. I do not now recall the exact load intended, but let's assume 3 drams. In black powder this would weigh 82 grains. Most smokeless shotgun powders weigh considerably less for an equal volume of black & while I have not actually performed a check weighing, just using figures from a Lee Dipper chart PB would have a wt of about 57% that of black. For a BP 3 dram volume it should thus have weighed about 47 grains. I don't have an IMR loadbook in front of me but this was likely approaching a double charge. Double charging with smokeless powders is not such a good idea. It is imperative to keep ones B's & P's in the right order.

It's like getting a head-start, reading from members who've read the great books. Thank you.

Miller, I also remember as you do. His conclusion was he'd never again have two different powders on the bench at the same time while reloading.

JC

Jim Legg & Jack +100..........

Well Doug . . . all of this remains in the "unknown" category, until someone does something like firing a 3" shell in a 2 1/2" chamber and seeing if the velocity increases vs a 3" shell fired in a 3" chamber. Both Sherman Bell and Arthur Curtis (the latter reporting in an American Rifleman article from 1936) did indeed fire 3" shells in 2 1/2" chambers--Bell in a 12ga pressure barrel, as part of his "Finding Out for Myself" tests, and Curtis in standard .410's with 2 1/2" chambers. Both reported blown ends on the shells. Bell reported the nearly 1500 psi increase in pressure. Neither, unfortunately, provided comparative velocity readings. Bell would not have noted increased recoil, since it was a pressure barrel rather than a shoulder-fired gun. Curtis reported no "trouble or great discomfort other than would be expected from the use of high-speed loads", and he apparently didn't bother to shoot the same 3" shells in a .410 of the same model, only with the appropriate 3" chambers, so that he could make an on the spot comparison of recoil. But we do have other reports of increased recoil from long shells being fired in short chambers, and while one would tend to say--given the major factors in how recoil is generated--that it must be due to increased velocity, we don't know that for sure without velocity measurements having been taken. On the other hand . . . with a blown end from the shell also going down the barrel, we have now increased ejecta WEIGHT vs the same shell without the end blown off. So that might be a possible explanation for a noted increase in recoil. Although not a lot of additional ejecta weight . . . who knows? Certainly easy enough to test for a velocity increase, using a .410 with 2 1/2" chambers, if anyone is willing to do as Curtis did and fire 3" shells in one of those.

Food for further discussion and experimentation . . . and truly unfortunate Jim Legg is no longer here to join in on the discussion.

"On the other hand . . . with a blown end from the shell also going down the barrel, we have now increased ejecta WEIGHT vs the same shell without the end blown off. So that might be a possible explanation for a noted increase in recoil. Although not a lot of additional ejecta weight . . . who knows?"



OK guys no sense guessing about the theoretical. To make life easy I have included a link to an automated recoil calculator. Plug in you numbers and find out for yourself.

http://www.10xshooters.com/calculators/Shotgun_Recoil_Calculator.htm

I think any increase in recoil that could possibly be attributed to a little bit of dislodged plastic will be negligible at best.

That's handy, thanks TwiceBarrel and "fly safe"......

Best Regards,

yall beatin dis won tu det...don u tink?

So would I, TB--but it is another factor. Right now, at least given any information I can find, the only things we know about long shells in too short chambers and/or in guns with very short and sharply angled forcing cones is that a) you can end up with blown ends on the shells; b) at least some shooters report increased recoil; and c) there is an increase in pressure, reported to be in the 1500 psi range in at least one case. We don't know that there's a velocity increase, which is the logical culprit in increased recoil, assuming shot charge weight stays the same. What we need is a volunteer with 2 .410's, one with a 2 1/2" chamber and the other with a 3" chamber. That'd tell us what we need to know about any velocity change. But unless the guns are identical in all other ways except chamber length, it would not be a good comparison as to whether recoil increases.

Since a shot charge should act as a fluid when passing from the camber/hull through the forcing cone to the constriction of the barrel we would probably experience a venturi effect where by when a fluid is compressed velocity of the fluid increases (PA24 we should have considered this earlier but your comment on flying sparked a memory from my days studying elementary aerodynamics). I really don't think that the amount of velocity increase is enough to translate to a perceptible increase in felt recoil but we may have some recoil sensitive folks out there that can detect an increase in recoil of half a foot pound or so.

Good Call Steve, yes "Bernoulli's Priciple" would take effect at any constriction which would act as a venturi and the charge would act as any fluid, as per Newton's second law pertaining to conservation of mass.....i.e. forcing cones and chokes......

Best,