Knockdown Power

[MachIVshooter]

The M33 .50BMG pushes a 668gr fmj down the tube to 2910fps hitting 12,550ft.lbs energy at the muzzle, but the recoil energy from it is somewhere in the 70ft.lb. neighborhood. Is the rest soaked up by the rifle?

Yes. It's the same concept vis a vis a rocket not pushing the earth out of orbit. .50 BMG rifles are heavy, usually ~ 30 lbs. That's 210,000 grains, or 314 times what the bullet weighs. While the calculation for free recoil is a little more complicated than using the weight differential factor applied to muzzle energy, it is not difficult to understand why the recoil energy is exponentially lower than the projectile energy.

If the bullet had the same mass as the gun & cartridge case, they'd both depart their static location at the same speed, in opposite directions.

 

[Zotter]

http://www.firearmstactical.com/hwfe.htm

Be sure to read the conclusion on page 19, 3rd paragraph - if nothing else.

 

[DoubleTapDrew]

it is not difficult to understand why the recoil energy is exponentially lower than the projectile energy.

That's why I don't understand the "If it doesn't knock the shooter down it won't knock the BG down" argument, assuming the round dumps all or most of it's energy in the target. I'm not saying I believe you can knock down a bad guy with a bullet, just don't understand the statement so oft repeated.
I can't imagine getting hit with 12k lbs of energy. Imagine it would at least sting a bit.

 

[LaserSpot]

Sure, there's the equal and opposite reaction but the bullet starts from rest and accelerates down the barrel, although it happens very fast.
The M33 .50BMG pushes a 668gr fmj down the tube to 2910fps hitting 12,550ft.lbs energy at the muzzle, but the recoil energy from it is somewhere in the 70ft.lb. neighborhood. Is the rest soaked up by the rifle?

It should be explained that Newton's equal and opposite law only applies to conservation of linear momentum. Momentum is proportional to mass x velocity. Kinetic energy is proportional to mass x velocity squared.

Energy can go any which way, in this case mainly from chemical energy to kinetic and thermal energy. Energy doesn't have a direction; there is no opposite energy.

 

[Stirling XD]

Here's an experiment. Offer to take your neighbor shooting. After a few shots with a 22, offer to put through an exercise to enhance his accuracy. Tell him to close his eyes and relax. THen hand him your .300 Win. Mag. and tell him to hold the butt of the gun to his chest and continue to relax. Then, very carefully, pull the trigger and see if it pushes him back any.

Keep in mind that those pulling the trigger are ready for the recoil while those getting shot aren't. I wouldn't be surprised to see stumble backward after getting shot. But I wouldn't expect to see them get blown through a window.

P.S. I don't recommend the experiment mentioned above, but it's fun to think about.

 

[duns]

What's the question again?

 

[Shadow 7D]

I believe the official response is psycho-somatic shock, OR
in plain speak
Self-Induced- shock

AKA
you fall over because your THINK you are supposed to..

50 cal can rock you, but it still doesn't "knock" you down, I've had friends that have been hit by shrapnel, things much larger than a bullet, one described it as a baseball hitting him in the SAPI, and that was directly over his spine, he went numb and fell down because he couldn't feel his legs, it just bruised his spine, he is fine today, but it that piece didn't do it, I doubt a .45 would.

 

[NWCP]

Film taken during actual combat shows quite graphically the effects of lead meeting the human body. The individual being shot with a small arm generally falls into a contorted heap upon impact and any movement depends upon where the unlucky soul was hit. Artillery, explosives, grenades and such are a different story altogether. The best one can hope for in an altercation involving handguns would be to either take out the central nervous system with his or her first shot, or inflict enough pain upon the intended target as to discourage any further desire to fight. I would actually prefer to avoid putting myself in the situation in the first place if at all possible. That is the best of all outcomes IMHO.

 

[Shadow 7D]

The same film also shows people being shot multiple times and not even breaking step, more than a few people have been shot only to find out after the firefight because they are bleeding, what happened to the "knock down" on them

the only certain knockdown is a CNS, CENTRAL Nervous System hit, A spine shot or a BRAIN shot, then you have bone shots, that shatter a bone, and even those aren't a sure thing. There is no mysterious Knock Down, Newton is correct, the force on the bullet is mostly equal to the force of recoil, so if the recoil can't knock you down, the bullet, after bleeding energy to friction, isn't going to do. PERIOD

THAT MEANS:
for a "knock down" you have to hit (ie AIM) for a CNS shot, everything else is happenstance.