>>>>knockdown power is a myth.
You can penetrate a human, but nothing remotely the size of a bullet can knock a man down.
You can penetrate certain parts. If you get his spine or brain stem he will fall, but will not be knocked down.
If you penetrate the heart or large blood vessels, comeing from it, the target will bleed out, but will not be knocked down.
Lavoisier the French Scientist who discovered oxygen was sentenced to death. His last experiment was to blink his eyes as long as possible after the knife cut his neck. It took 16 seconds for that head to die....<<<<
Knockdown power is not a myth. It is directly related to a size, shape of ammunition and muzzle velocity.
Learn about kinetic energy.
If it knocks a man down when it hits, simple physics says that it will also knock the firer over when discharged. Learn Newton’s Laws.
Kinetic energy is a fine thing. Yet a bullet that misses has the same amount of kinetic energy as one that hits. Energy lost when a bullet penetrates the back does no damage. Some structures in the body are necessary life, others are necessary for volitional action. Miss an important organ, and you don’t end its function, perhaps ever, perhaps only indirectly after a slow process of bleeding out. The spine is nearly the length of the torso, but also only the width of the tip of the little finger. Even when missed, psychological conditioning (Oh, I was shot, I should lie down!) can lead to greater effect than what biology would expect, or less. One gentleman took a 40mm grenade through the chest, and lived. Another had a crowbar blown through his head by a premature charge, and survived and recovered. Kinetic energy? both had plenty, and survived, the latter without ever losing consciousness!
Because of the complexity of the human target, simple measures such as kinetic energy give misleading estimates of bullet effect. If you care enough to give your very best, care enough to put a few rounds in every identified target.