In late 2009 wrote I an essay supporting an heretical (to many gun owners) theme: "My conclusion from researching the subject and consulting physicians and other experts is that no ordinary firearm has dependable stopping power."

[NOTE: This does not mean that handguns are useless for self-defense. Criminals are looking for the vulnerable and the helpless. In the great majority of cases when a victim pulls a gun criminals flee. They have no interest in a gunfight. It gains them nothing and puts them at two terrific disadvantages: 1) gunfire brings police attention; 2) if criminals are wounded they either forego medical attention or go to a hospital and then to jail.]

My negative conclusion about stopping power and many of my facts came from the research of retired Col. Martin Fackler, MD, an experienced combat surgeon who after Vietnam went on to found and head the Armed Forces Wound Ballistics Laboratory. He has now written me correcting sme of my statements. Hee is his letter:

First, your 12th paragraph (ANY bullet in the head will incapacitate, etc): If you write "most center-fire rifle bullets that enter the central area of cranium, at a range under 100 yards, will immediately incapacitate"; you come a lot closer to the truth. If you wish, I can possibly find the reference, in the medical literature, to collected head shots -- as I recall it was from a source in Europe, in the past two decades I think --in which more than a few shots, from handgun bullets, that penetrated the cranium did not cause immediate incapacitation.

Recounting instances of multiple-shot-outcomes misses the point: which is what structures were disrupted by the shots? Go to an anatomy text and find a view of the human body from the front -- in which all the organs, bones, blood vessels, etc. are shown. Then note how much of the body's frontal area a bullet could hit and pass through without hitting any significant blood vessels (the heart is a modified blood vessel), the brain, or the spinal cord (or bone of the spine within an inch of the cord).
Certainly it is more than 75%. All those shots through loops of bowel, lungs. The liver, kidneys, spleen, various muscles, etc. can't be counted on to cause the determined assailant to stop his aggression in the next few minutes. Even shots hitting big blood vessels, with the possible exception of putting a large hole (at least half the diameter of the vessel) through the aorta in the chest are unlikely to stop aggression in less than a minute.

I would add to the FBI doctrine: "if he still has a gun when he hits the ground you might want to continue firing; and certainly if he points it at you while on the ground - fire!

Better than Newton, simply ask how many deer get knocked down by rifle bullet hits? In my meager experience of shooting six of the small German Reh deer through the big blood vessels just north of the heart (German hunters sell the meat -- and the heart is meat) with a .243 Winchester --all just ran off giving no indication of being hit --to be found dead within 100 yards. In no case was a deer's body displaced noticeably by the bullet.  Suggest any doubters prove it to themselves by filling a large sack with 160 lb of dirt, hanging it from a tree limb, noting how easy it is to move with a shove from your hand, steadying it, and shooting it. They will observe the lack of significant movement.

Pete Kasler shows photos of shots into a 170 lb free swinging bag shot with a 10mm handgun bullet at a distance of a few feet: the max rearward deflection was "about 3/4 inch." (Kasler PA, Business Partners, Paladin Press, 1991, pp 12-13).

The Am Rifleman demonstrated this lack of movement, as I recall, in 1906 They cut out two frontal outlines of a human body from plywood; spaced them about 8 inches apart, and put in some side walls; filled it with sand, and glued it to a small platform which had roller skates on its undersurface. Hits from a 30-06 moved it about two inches.