Does recoil amount and velocity affect muzzle velocity?

toddc

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Ever throw a 22lr into a fire? The bullet stays put and the case flies off into the dark.

If we vary our HOLD on a rifle, will the muzzle velocity vary? Law of equal and opposite reaction would seem to say YES. However many people say NO.

I can buy that some of the energy is being directed in a radial manner in stretching the chamber and brass, BUT some of the energy is transmitted thru the lugs into the stock . If that energy has a VARIABLE resistance to it, then wouldn't the muzzle velocity vary as well? I realize that much of the recoil impulse is transmitted to the shooter AFTER the bullet has left the barrel, however there would still be a variance WHILE the bullet is in the barrel.

If you fire a cartridge from a gun that weighs LESS than the bullet and then added 20 lbs there would be a variance in MV. If this holds true, then our HOLD can also vary MV. And yes I am sure the difference would be SMALL but as someone who is looking for an ES under 5fps then it could definitely matter. 10FPS is plenty at 1k to miss a prairie rat OR target.

This is a question. I am not saying I am right. Honestly it seems impossible to BREAK a law of physics.
If recoil velocity varies within a system then according to physics the MV should vary as well. Or am I nuts? AGAIN.:)
 

gohring3006

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I would test it with a Chrony. Next time you're at the range, shoot the rifle against your shoulder, and shoot it against a post or something that will not move... I'm guessing you won't see a change. Mainly because the bullet is long gone when the rifle recoils.
 

tbrice23

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The rifle is recoiling as it moves down the barrel and recoiling more as the gases push on the crown. The lack of detectable velocity loss during free recoil in my 6BR is because the **** rifle weighs exactly 17lb.
 

FearNoWind

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If we vary our HOLD on a rifle, will the muzzle velocity vary? Law of equal and opposite reaction would seem to say YES. However many people say NO.

No

I can buy that some of the energy is being directed in a radial manner in stretching the chamber and brass, BUT some of the energy is transmitted thru the lugs into the stock . If that energy has a VARIABLE resistance to it, then wouldn't the muzzle velocity vary as well?

No - Muzzle velocity has nothing to do with recoil. The pressure affecting muzzle velocity is a factor of the pressure that developes between the fired cartridge (captured in the chamber) and the projectile leaving the cartridge and passing through the bore and out of the muzzle.

I realize that much of the recoil impulse is transmitted to the shooter AFTER the bullet has left the barrel, however there would still be a variance WHILE the bullet is in the barrel.
If you fire a cartridge from a gun that weighs LESS than the bullet and then added 20 lbs there would be a variance in MV. If this holds true, then our HOLD can also vary MV. And yes I am sure the difference would be SMALL but as someone who is looking for an ES under 5fps then it could definitely matter. 10FPS is plenty at 1k to miss a prairie rat OR target.
This is a question. I am not saying I am right. Honestly it seems impossible to BREAK a law of physics.
If recoil velocity varies within a system then according to physics the MV should vary as well. Or am I nuts? AGAIN.:)

Yes -


Well, maybe not nuts. But you must have missed a few hours of the physics classes. :rolleyes:
 

Edd

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I have read comments made by Bart B that said using the same rifle and ammo but changing shooters could cause a 50 fps change in velocity. I think he should know. Now that I've thought about it, I think he said 100 fps.
 

toddc

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No



No - Muzzle velocity has nothing to do with recoil. The pressure affecting muzzle velocity is a factor of the pressure that developes between the fired cartridge (captured in the chamber) and the projectile leaving the cartridge and passing through the bore and out of the muzzle.



Yes -


Well, maybe not nuts. But you must have missed a few hours of the physics classes. :rolleyes:

I did miss a few physics classes but I did pick up on the equal and opposite reaction stuff, if the pressure is captured in the chamber and the bullet is traveling forward then the felt recoil is the reaction to the forward motion of the bullet. If the rearward reaction varies in intensity, then the forward motion should as well unless it is proposed that the gas CUSHIONS the bullet. Even a cushion effect would still result in a varying velocity.
 

toddc

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I have read comments made by Bart B that said using the same rifle and ammo but changing shooters could cause a 50 fps change in velocity. I think he should know. Now that I've thought about it, I think he said 100 fps.

You know I remember that as well. Someone wrote a paper on it. Will see if Google works. Thanks for jogging my foggy brain.
 

toddc

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I have read comments made by Bart B that said using the same rifle and ammo but changing shooters could cause a 50 fps change in velocity. I think he should know. Now that I've thought about it, I think he said 100 fps.
Cant find that article. However did find some pretty cool physics boards and it does turn out that adding resistance into the recoil of the firearm WILL AFFECT VELOCITY. Adding mass to the gun or mass to the shooter or placing the gun against a large object will in fact increase the muzzle velocity or if recoil mass is removed decrease muzzle velocity. They used placing the gun against the ground as an example and even went so far as to say that the recoil would move the earth which is what the equation would show.
 

Greyfox

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I have shot my 300WM with and without the muzzle brake and MV/ES is identical. My hold was constant. Recoil without the brake will loosen my teeth. With the brake its lighter then my 308. I'd say no.
 

catamountsierra

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I am quite certain that it would change the muzzle velocity; the basic physics says that it should. My question, for those who have a better chrono and more time than I have, is this: is the difference measurable or significant enough to make a difference? When it comes down to it, we are not dealing simply with force but with impulse, or force multiplied by time. The physics would say that having a bulky jacket would reduce the muzzle velocity, but would it be a significant amount? Or would it be well within the SD or ES that we expect and therefore not measurable or significant?
 

toddc

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To make this easier to understand, if a projectiles MASS = gun weight, the two will move away from each other at exactly the same acceleration. So if your gun weighed 300 grains and you shot a 300 grain bullet....well it would blow thru your shoulder. Since your gun weighs much more than the bullet and kinetic energy is a function of a square of velocity, when you pull the trigger the gun doesn't blow thru your shoulder.
Physics is physics. The velocity variation may be small and is in fact exactly equal to the recoil velocity of the gun/shooter. If a HARD HOLD changes recoil VELOCITY by 10FPS then there will be a 10FPS difference in bullet velocity. Changing HOLD RESISTANCE by 30 LBS with a 3000FPE 3000FPS bullet will affect velocity by over 20FPS.
All of the physics are online and available for all to see, as well as the calculators to figure the differences.It looks like a lighter rifle will be affected more than heavier and larger charges and bullet weights are more susceptible to differences.
Just one more reason to be as consistent in shooting as possible.
 

toddc

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I am quite certain that it would change the muzzle velocity; the basic physics says that it should. My question, for those who have a better chrono and more time than I have, is this: is the difference measurable or significant enough to make a difference? When it comes down to it, we are not dealing simply with force but with impulse, or force multiplied by time. The physics would say that having a bulky jacket would reduce the muzzle velocity, but would it be a significant amount? Or would it be well within the SD or ES that we expect and therefore not measurable or significant?

I am afraid of a lead sled and a scope and I don't have anything without a scope. I was thinking a Magneto would be best to test this, however if you plug #s into a recoil calculator. The recoil velocity shows that the difference in mass MASSIVELY AFFECTS recoil VELOCITY which is what matters. Looks like a 20 FPS difference is POSSIBLE depending on the case involved and gun weight versus human weight.

Recoil Calculator
 

catamountsierra

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I am afraid of a lead sled and a scope and I don't have anything without a scope. I was thinking a Magneto would be best to test this, however if you plug #s into a recoil calculator. The recoil velocity shows that the difference in mass MASSIVELY AFFECTS recoil VELOCITY which is what matters. Looks like a 20 FPS difference is POSSIBLE depending on the case involved and gun weight versus human weight.

Recoil Calculator

My understanding is that the momentum of the system remains constant, not the velocities. This means that the magnitude change in momentum (mass*velocity) of the bullet is equal to the magnitude of the change in momentum of the rifle (and likely the shooter as well); directions should be opposite or you will have the recoil pull the rifle off target by some amount.
I need to think about this. You have posed a puzzle and I am intrigued. Now I know what I can work on while I wait for my computer at work. If my poor concussed brain wasn't so tired, I might try tackling this tonight, but I think it will have to wait for tomorrow. I haven't tackled a question like this in a while and I think I am looking forward to it; does that make me crazy?
 

bigngreen

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It's absolutely how it works, we've seen at benches with guns that you can run free recoil but then put a hard hold on them and your velocity changes. Shooting with a muzzle brake on and of will be the same because that only effects recoil that happens after the bullet levels, it's how hard you hold the rifle during recoil with the bullet in the barrel that will show up.

Perhaps a search would yeild some info since we go through this every couple years.
 
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