doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Pattern theory

So you put a guy on his back, legs and hands up, like an upside down dog�

Then you have him support an 8� dia. piece of plywood on his hands and feet.

Then you spread 30lbs. of square shot (so it does not roll off) evenly on the board.

Then you ask him to lower the board and push up as fast as he can, and then ask him on a scale of one to ten, how hard it was.

Take the same guy on his back, except with a 4� dia. piece of plywood (of a thickness that equals the same weight of the 8� dia.) and place the same thirty pounds of square shot on the board.

Then you ask him to lower the board and push up as fast as he can, and ask him on a scale of one to ten, how hard it was.

All things being equal, he used the same energy and force (other than the extra air resistance for the larger dia.)

In other words, he did not have to be stronger to push the smaller dia. board that was carrying the same weight/mass.

Right?

CraigD - "that more pounds could be shown to push on less square inches of a smaller bore to end up with the same velocity for the same weight of shot. "
More pounds are not pushing on fewer square inches. The same pounds are pushing on fewer sq. in. Thus, total force the same, but force per sq. in is less.
Some other questions come to mind. How far up the shot column does the "force" cause the pellets to become deformed? What happens if, instead of a column of individual shot pellets, you have a lead cylinder of the same weight? When, and if, does a shot column begin to behave like a solid lead cylinder?
There are fewer pellets in each cross sectional area of the smaller gauge, so fewer pellets on the "bottom". Does this decrease in number have an effect on total deformed pellets? If both the small gauge and the large gauge were fired from a cylinder bore, would you get a greater dispersion from the smaller bore because of deformed pellets becoming outliers from the main pattern. Think about what happens if you carry this to absurd extremes - that is, bore size is decreased until it equals pellet size or increased until you have just one layer of pellets.
I think there is much that is not known about the process. There is no shortage of opinions, anecdotal evidence and some non-controlled empirical evidence. I'm biased toward theoretical constructions validated by evidence from controlled repeatable experiments, which is what I think Wonko was saying.

When I wrote my arguments here I always tried make them apply to just the shot. You can get into the mass of everything being ejected - shot, wad, burned powder and hot gasses. You can get into the energy expended in deformation of the wad, the deformation of the shot, the heating of the shot, the heating of the barrel, the opening of the crimp, bore friction etc... But the great bulk of the work is expended overcoming the inertia of the shot charge in order to accelerate it from 0 to 1200 fps.

cpa we are interested in the deformation of shot because it is accepted that deformed shot affects patterns and causes shot stringing.

In your example of a barrel with a bore diameter equal to diameter of a single pellet, say #8 and one ounce, the bottom pellet of that shot charge would be under much higher stress than a shot on the bottom of a shot column of 1 ounce of #8s in a 12 gauge. Just like the feet of the bottom acrobat in Case 2.

Isaac Newtons laws of physics, at the velocities we are talking about, are the theory, and much of the modern technology has developed using them. People like Bob Brister and John Olin and Tom Armbrust have done the empirical experiments that validate shot stringing and shot deformation. They proved that harder lead shot (with antimony) strung less that softer shot. The theory being that it deformed less and so had a lower coefficient of drag than shot that was more deformed. The painted shot test proved that the bottom third of a shot column deformed more than the top layer. So the experimental confirms what the laws of physics predict.

If you build a shotgun where one ounce of #8s will cover the bottom of the wad in one layer you will have much less stress on that single layer shot compared to your shotgun with a diameter of one #8 pellet shooting one ounce of #8 shot. I suppose the shot column in the cartridge could be 6" long!

In your theoretical shotgun with a bore diameter equal to a #8 pellet the pellet at 1/2 the length of the total shot column length will see the 1/2 of the stress of the pellet at the bottom of that shot column.

Mike, I don't think it as cut and dried as you believe, nor have many of the ideas been "proven" by controlled repeatable experiments. Probably time to put it to bed, as the horse has been beaten long after it died.

Shot stringing has been validated experimentally by John Olin and by Bob Brister. The effect of hard shot and buffering on shot stringing has been validated by Brister and John Olin and Company. Could you point out what it is that John Olin did wrong or Brister did wrong?

You do accept Newtons laws of physics for the velocities we are talking about, right?

I've never had any disagreement with shot stringing, although the exact process probably has some variability and unknowns lurking about, and the consequences are subject to debate. After all, a shot string six feet long @ 900 fps will all reach the target in .0067 seconds. A bird flying across at 35 mph will only move about 4" during that time if my quick calculation is correct. If you have a 30" evenly spread pattern, that is pretty inconsequential. My whole discussion was based on disagreement with the comment that the force required to move a 1oz. load in a smaller gauge was greater than in a larger gauge. You have agreed that is the case.

I thought this was settled up front? It did get a little convoluted when the word pounds was comingled in different applications.

I think we agree that it takes some force to distort shot. Earlier high speed photos show not only shot stringing, but, as pointed out, flyers that left the shot string, regardless of choke. Maybe meaning that something happened to the integrity of some spheres before they cleared the barrel.

As to pellet packaging in a shell, we know what happens when all the pellets are squished together with no voids, it behaves like a single bullet. It's easy to look up how spheres like to align themselves. Chances are, if the force on them is equal as you mention, then the total distortion to the shot in any form will be equal. As the good doc mentioned pages ago, spheres that have a higher percentage of their surface area damaged are less likely to fly true. Maybe the spheres that have less points contacting them will have all of the force created distortion concentrated on those lesser contact points. The doc made a very generous offer to run tests for a fee, but he already offered foregone conclusions for free.

cpa:

The energy/work applied to ounce of shot to accelerate it from 0 to 1200 fps is the same whether it is applied in a 12 gauge or a 28 gauge. There may be minor differences in the efficiency of the energy used to apply that energy to the shot charge but they are most certainly very small.

The shot at the bottom of that 28 gauge shot column will experience more stress than that shot at the bottom of the 12 gauge shot column. Thus the 28 gauge shot is more likely to be deformed.

There are tables that show how long it takes a given size shot to travel a given distance, based on a particular muzzle velocity.

It seems that it is the nature of most firearms enthusiasts to always strive to increase the effective range of their chosen weapon. Over the last 150 years, in pursuit of that goal, choking was developed. Then progressive powders allowed an even larger charge of shot in the same gauge. Shot cups and pie crimping were developed with the aim of getting more effective range from a given shot charge and muzzle velocity.

So if I don't have any "fliers" losing velocity and drifting out of the pattern before they arrive at the target I have more pattern density. Given the correct choke I now have extended my range.

#9 shot runs out of penetrating power before it runs out of pattern density. #4 shot runs out of pattern density before it runs out of penetrating power.

Shot stringing lowers pattern density at the target and thus the maximum effective effective range for a given combination of shot weight, muzzle velocity, and choke. If you don't think so imagine a shot string fifty yards long.

If you load one ounce of hard 5% antimony shot into a modern plastic shotcup in a shot shell and then optimize the choke selection you can get a longer effective range than if you pour 1 ounce of the same size soft lead shot onto a fiber wadded shot shell and then put a shotcard on top of that and roll crimp it. Again with an optimally selected choke.

I shoot mostly trap and bobwhites (over pointing dogs). I am not worried about shot stringing or extending range. But I find the theory and the experiments and the discussions and articles about it very interesting and follow them closely. I shoot competitive trap but I don't win, place, or show very much. I only shoot 1-1/8oz of #8s with a muzzle velocity of 1145 fps (2-3/4DE). But I buy the cheapest shell I can because I believe, at my skill level, shot stringing isn't responsible for any of my misses. My favorite trap choke is mod.

My favorite load for bobwhites is one ounce of #8s. Again I don't worry about shot stringing. My favorite choke for bobs is cylinder. But I don't worry if about the length of the shot column whether I am shooting that one ounce of a 20ga or a 16ga or as 12ga.

But if I was shooting for big money at pigeons or hoping to shoot bunker trap in the Olympics or hoping to win my Regional ATA championship I would pay much attention to shot hardness, bore diameters, and overall shell quality. Because shot stringing affects maximum effective range and quality of patterns.

I thought I had made a post on this earlier this AM, then had to leave. It's not here so obviously didn't go.
Based on figures in an old Hercules loaders manual for a shot of unknown size or hardness the give .288 Cu In as the volume of 1 oz of shot. In a 12ga bore of .729" this gives a column length of .690", in a .550" dia 28 ga a length of 1.212" or 75.7% longer.
Now if you truly believe that Force, Mass & Acceleration is the total story, then drop 23 grains of Red Dot in a 28ga hull, put on necessary wadding & top it with 1 oz of shot & a good tight crimp & Touch'er Off in an old decrepit gun of dubious quality, folks have been doing it for years in 12 gauges & after all the Force is the same, the Mass is the same so Acceleration should be the same. Only difference is a matter of applying it over .2376 sq inches of bore rather than.4174 sq in. After trying this simple little experiment "IF" you still have fingers to type with & can see the keyboard report your findings back to us.
The "inertial" resistance to being moved incidentally is the same in the 1oz 28 gauge load Per Sq In as it is a 1 3/4oz 12ga load for they have essentially the same column length.