I found this to be a very interesting and informative read.
Handgun Wounding Factors and Effectiveness
My son and I have had this discussion before, I disagreed with him. It turns out he was right all along.A bullet simply cannot knock a man down. If it had the energy to do so, then equal energy would be applied against the shooter and he too would be knocked down. This is simple physics, and has been known for hundreds of years.31 The amount of energy deposited in the body by a bullet is approximately equivalent to being hit with a baseball.32 Tissue damage is the only physical link to incapacitation within the desired time frame, i.e., instantaneously.