> Have you been in the Military?? If not your not likely to understand the truth of thing simple as that. Full metal jacket is design to wound more often then kill but yes it will kill if hit in the right place. As for how fast the bullet goes that again has to do with kinetic energy. A M-1 carbine bullet is a small light bullet where as the 357 if a heavy bullet an slow and heavy and slow means more kinetic energy. That is why the colt 45 was produced due it high kinetic energy and being a hard hitting round and was said to knock a man down even if hit in the hand. That statement is as told to us in boot camp by the way
I spent a decade of my life working on military installations alongside US servicemen. Not that military experience is a substitute for an education in classical physics, as evidenced by your post.
You are confusing energy and momentum. Energy equals 1/2 mass times velocity squared (1/2mv2). Momentum equals mass times velocity (mv). In practical terms, this means if you take two bullets, one light and one heavy, and drive them to the same muzzle energy, the heavier bullet will have greater momentum. Back when the 45 ACP (I think you meant 45 ACP rather than 45 Colt) was introduced, it was believed that high momentum translates to higher "knockdown power", but most folks agree these days that momentum is not as big of a factor in lethality as energy. On the other hand, momentum is important for metallic silhouette shooters who want their bullets to knock down targets rather than punch through them.
Let's compare three cartridges: .30 Carbine (110 grain bullet), .357 Magnum (158 grain bullet) and .45 ACP (230 grain bullet). Velocity is from Wikipedia, while energy and momentum were calculated using the Taylor KO Calculator.
.30 Carbine: Muzzle velocity = 1990; Muzzle energy = 967 ft-lb; Momentum = 31 lb-ft/sec
.357 Magnum: Muzzle velocity = 1240 ft/sec; Muzzle energy = 539 ft-lb; Momentum = 27 lb-ft/sec
.45 ACP: Muzzle velocity = 835 ft/sec; Muzzle energy = 356 ft-lb; Momentum = 27 lb-ft/sec
Interesting: The lowly .30 Carbine cartridge has both the greatest muzzle energy AND the greatest momentum. And the slow, heavy .45 ACP comes out dead last. In fact, the only advantage the .45 has is it makes a really big hole. Which isn't much of an advantage if it has to penetrate body armor.