Here is a video of a man shooting himself in the chest with a 44 magnum. He follows it up by shooting a man in the chest with a 308 WIN rifle who happens to be standing on one leg. Neither man moves a muscle (they do have some serious faith in the products though). I laugh when I hear knockdown power. If a 44 magnum and a 308 WIN can't "knock down" a man, a 9mm or 40SW sure can't. Heck, even a 45 ACP might not be able to do it.