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Originally Posted by russ_watters
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Originally Posted by Colt
Ripper, one of us might want to explain how a bullet impact works, the physics of it and what it does on penetration.. Of course I'm not sure if the BA would like that or not. -Colt
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I'll give it a shot (so to speak). On a shot with an entry and no exit, all the momentum of the bullet is transfered to the victim (minus whatever is absorbed in its fragmentation). So the victim responds similar to if punched. They don't fly through the air like in the movies though.
In a head shot with an explosive exit wound, the matter exploding away from the bullet may well have more energy than is absorbed by the entrance wound. That is simply a property of collision kinematics. The best analogy I can think of (though not a perfect one) is hitting a golf ball - the ball doesn't travel at the speed of the club-head but at the speed of the club-head plus a percentage of the speed of the club-head as determined by its and the ball's elasticity. So that explosive exit wound is carrying more momentum than you might think - and it is carrying momentum away from the head. So action-reaction: the head moves in the opposite direction. |
It has been said that Kennedy's head jerking back was a muscle reflex. If you watch the Zapruder film you will notice a split second delay between the hit and the motion of the head. Again, a 6.5mm FMJ bullet will not impart much momentum to the target.
I have also seen the experiment I mentioned earlier that the expelled mass of the exit wound would have more momentum than the bullet can impart, causing a reaction in the other direction.
Most people, who know most of what they think they know about firearms get their information form movies. I can tell you that if you saw something about firearms in a movie it is 99% likely to be wrong. I saw a guy get hit with a .50BMG round. It did not knock him down, he just dropped in place. Given that, I do not think any conventional firearm would knock someone across the room like they do in the movies. It is simple physics. When you fire a gun you are launching the bullet and the propellant. Lets say a .30-06. That would be a 150 grain bullet and about 60 grains of propellant. Launching all of this out of the barrel at about 2900 fps generates about 4000 ft/lbs of energy, but since some of this is the propellant gasses (which by the way will come out faster than the bullet once it clears the bore, but I ant to keep this simple) the bullet is carying less than 3000 ft/lbs. Depending on range, the bullet will have imparted some of its energy to the air by the time it hits. Now, even a soft point bullet from a .30-06 will not impart all of its energy to a person's body at less than extreme range. The bottom line is that the firer is taking a lot more kinetic energy than the target. The mass of the rifle will absorb some of that, but 10 lbs of mass would not make much difference. The firer could easily have 10 lbs less body mass.
OK I have gone on long enough.