doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com How to calculate felt recoil

For a mere $499 you can have this basic set up, If you would try, an experiment with a Browning BOSS rifle you could readily switch between the muzzle brake and non - brake, You could see if it makes a difference.

Or you could shoot a gun enough to get good data, have your gunsmith lengthen the forcing cones and then shoot it some more. We could determine what is snake oil, and what has some potential.



http://www.shootingsoftware.com/recoil.htm

In calculating recoil, the effective muzzle velocity of powder gases can be significantly higher than the velocity of the shot and wads. It is estimated at 1.5 times shot veloctiy in "Hatcher's Notebook". This is based on similar results for 30/06 type military rifle cartridges. Apparently, once the shot and wad, or bullet, leave the barrel, the gases previously trapped behind them expand rapidly and leave the muzzle at high velocity. The 1.5 factor can have a noticable effect on computed recoil.

Recoil can certainly be measured. They had pendulum devices more than 100 years ago. But "felt recoil" at least the highly questionable types can not be measured(to my knowledge) because much of it is the perception of the shooter, often times no more than wishful thinking. This, of course, is the way the SOS(snake-oil salesmen) want it. If the effectiveness, or lack of, in their illogical claims could be measured, the truth would be known. The results of adding a recoil pad, a recoil shock absorber in the stock and the effect of gas autos probably could be measured but these are all well accepted legitimate reducers of felt recoil, with physics on their side. There may be a few others I'm not thinking of but these are the most common ones that everyone would agree on(I hope!). Any sane person can feel the difference between an 8 lb. O/U with a plastic buttplate and an 8 lb. O/U with G-squared or J & S Air Cushion device in the stock. If 5 people believe they "feel" a difference now that they've had their 1" forcing cone lengthened to 1-1/2" and 5 people say they feel no difference after they had the same operation done to identical guns, why would that be? If it's real, why don't they all tell the same story? My conclusion is the first 5 are believing what they want to believe.

Oh I agree with you about the forcing cones. and many of the others

A pendulum only measures recoil energy - which can be calculated. I'm still thinking that peak recoil force is as important as total recoil energy.

Just at the point where the wad is ready to exit the gun's muzzle the bore will be "Full of Gas", thus you could say half of it has moved the length of the bbl. If we take a 1 1/8oz load with a 35 gr wad & 24 grain powder charge, then we have a total wt moved to muzzle of .077lb. Ignoring the fact the wad is somewhere ahed of the breech to start, just figuring on the full length of a 30" bbl & a 7 lb gun, then just as the wad clears the muzzle the gun will have moved .077/7 x 30 = .330". The exit of the gas will give it a little more impetus, but not a lot. In this slightly over 5/16" of movement, acquired in around .003 of a sec, it will have attained it's recoil velocity & be carried on back my inertia.
With "All" other aspects of the gun being equal "Any" difference you can "Feel" can be "Measured" as it will come from either a significant change in either wt of ejecta or velocity of eject or both.
As Jim has so well pointed out recoil pads, gas autos, stock fit etc, which can & do, effect felt recoil are external effects which do not take place inside the bore of the gun.
While we talk of fast vs slow shotgun propellents, in the overall scheme of things they are "All Fast".
Maybe, just maybe, if you could get a charge of 5010 machine gun powder, or similar, to burn properly behind a 1oz load of shot the acceleration rate would be changed enough you could actually feel it. Within the range of suitable powders for a given load, I "Very Seriously" doubt it can be felt by a mere human. To Measure this difference would require equipment which not only measures total recoil, but rate of acceleration (probably doable in a large ballistics lab but maybe not worth the effort at present).
As again Jim has so well pointed out there are a lot of good salesmen out there who play on the "Unmeasured" aspects of recoil.
There are a lot of things which are totally "True" in "Theory" but from a practical standpoint are "Absolutely Insignificant". This is what the snake-oil-salesmen prey on, just a hint of theory that folks don't think through.

Friends:

The gas pressure at the muzzle is something like 80 psi - perhaps less. Remember the experiment performed by W W Greener, spoken of recently on this board, where he turned down the muzzles of a gun until almost foil thin, shot them successfully with no deformation, and then cut them off with a pen knife?

In reference to MG Hatcher's experiments with the .30-'06, You cannot generalize from rifles with breech pressures in the 55k psi range to shotguns with pressures in the 10k psi range.

Inertial recoil reducers such as "Dead Mule" work, because they spread out the recoil, or make time "t", go from very small to somewhat longer, which makes the perception of the recoil blow to be lesser.

I suspect the way to get from free recoil and its "Ke" calculation to felt recoil is to include a " time" component. It seems to me, Ke is "instantaneous". If the blow is spread out over some period of time, the ability to take that into consideration may get us closer.

Just ideas.

Regards

GKT

Greg,

The blow is (practically speaking) instantaneous if you are on the other side of the gun...

Here is an experiment to try only in your head, a thought experiment not a real life one (for obvious reasons.)

Remove the barrels from a gun and Weld a steel plate on instead. Make sure that the total weight is equal to the gun with barrels on. Shoulder the "gun with steel plate" as if you were going to shoot. Now imagine someone else standing a couple feet away fires another gun directy at your "gun with steel plate."

Ignoring safety factors, who would you rather be? Which gun do you think would "kick" more?

I'm betting that the "gun with steel plate" will "kick" a lot harder than the gun firing. Maybe I'm wrong, I'm not going to try it out just to see though.

http://www.clayshootingusa.com/readers/archive/jan_feb03/Recoil.pdf

and

http://www.clayshootingusa.com/readers/archive/jul_aug06/A%20Look%20at%20Recoil.pdf

Are a couple of articles from ClayShootingUSA that deal with felt recoil.

My guess is that if the hypothetical gun with the steel plate welded on weighs the same, the recoil will be about the same. Reason being that the received force is the same as the firing force being reacted to by the first gun. That's what causes the recoil the first shooter feels. I'd be interested to hear why you think the person with the gun/plate will feel more recoil?

To J. Hall,
I read and saved both articles. Interesting reading but nothing really new in either one. The first, not sure who wrote it, claims to have had help from Dr. Robert Birch. This article ends with pictures of Anthony Matarese, Jr. Under the second picture are the words "a well fitted gun, good grip and the correct placement of the butt into the shoulder can help reduce the effects of recoil, Our two pictures here, of Anthony Matarese Jr. illustrate the point-but also note the lack of tension in the right arm and hand". What was more noticeable to me, was that Anthony(while clearly an outstanding shooter) had the butt out on his shoulder muscle and very low on his pectoral muscle(not up and inside the shoulder pocket, as it should be). His neck and head was down, like a heron about to spear a fish, rather than upright, with the gun brought up to his face.
The second article, by Larry Nailon fell apart for me when Larry started talking about how variations in pressure "directly relates to a variation of actual recoil". As most of us know(I hope) pressure has nothing, zip, zero, nada, to do with recoil unless it causes velocity variations. Even then, it is the velocity variations, not the pressure that affects recoil.