From the FBI Firearms Training Unit:
"Barring a hit to the brain, the only way to force incapacitation is to cause sufficient blood loss that the subject can no longer function, and that takes time. Even if the heart is instantly destroyed, there is sufficient oxygen in the brain to support full and complete voluntary action for 10-15 seconds.
Kinetic energy does not wound. Temporary cavity does not wound. The much discussed "shock"
of bullet impact is a fable and "knock down" power is a myth. The critical element is penetration. The
bullet must pass through the large, blood bearing organs ..."
And yet people have been shot in the brain on occasions and still didn’t loose consciousness and survived. So that pretty much ruins that affirmation. Unless a very fast rifle round with a center of the head hit or a hollow point projectile turn the brain to pulp, there's no 100% assurance that a head shot will stop an attacker immeditaly for sure. Again, it still defends on where it hit precisely and with what caliber.
Here’s my offer, let me hit you once in the face, chest, stomach, or even a good kick to the thigh.
If you are still standing we can discuss the “myths” of kinetic energy some more. :^)
If as you say temporary cavity has no implication, there would be no difference between 38 special, 9mm and 45 ACP, all with round nose ammunition, since the permanent cavity is almost the same in all three in spite of the slight difference. Yet 45 hardball is clearly a superior stopper, based on street results.
That information is dated and it is abundantly proved wrong by empiric evidence. As I mentioned, a shoulder shot putting an attacker down for good, a gut shot with a .32 long dropping an attacker armed with a knife instantly, shock by 12 ga. LTL plastic pellets shot at contact range, even without serious penetration the shock was enough to leave the soccer player unconscious on the ground instantly. Trauma kills, kills all the time.
Seriously people, we can debate until the end of time, but some things are not opened up for debate:
1)Not all calibers are equal
2)Some have better one shot stop rates than others
3)Not looking into those rates and taking them into consideration is a pretty stupid idea.