
Originally Posted by
Liko81
The various calibers employ different theories in what causes the most damage, and are chosen over other calibers by people who subscribe to the theory. Of the 4 you listed, 9mm and .45ACP are the two most conflicting, and deal with penetration (deep wound) versus permanent cavity (big hole). Penetration and permanent cavity are the two most crucial elements of a handgun wound; when either of these is increased, so is the severity of the wound. There are however practical limits, and the two elements tend to be inversely related; increase the size of the bullet and it will damage more tissue, but require more energy to get up to speed and lose that enerrgy faster. A smaller bullet makes a smaller hole, but requires less impulse (meaning less recoil) to go faster. Neither is wholly wrong, and neither is wholly right; both sacrifice some factors in order to increase others; increase wound size with a bigger caliber and you must either decrease penetration or increase recoil. Increase penetration and you must either decrease diameter or increase recoil.
9mms operate with a small bullet travelling very fast; the idea is to get sufficient penetration to reach vital organs and the central nervous system. The downside is that the hole made is smaller, so a slight off-hit may not contact a vital organ or blood vessel, which a bigger round shot in the same place would have damaged. Hollow-points, which are the mainstay of 9mm defense rounds, alleviate this shortcoming, as does the reduced recoil which allows a shooter to make more accurate holes more quickly; 2 holes are better than one.
.45ACP rounds are 1/8" bigger out of the barrel and twice as heavy. The energy of the bullet is in its mass, not its speed. It makes a big hole, and does so even with ball ammo; no expansion required, making your "plinking" FMJ rounds highly effective defense loads if that's what's handy. The downside is that to achieve acceptable muzzle energy, a heavy bullet needs a big powder charge meaning increased recoil and reduced fire rate of aimed fire. It also penetrates less even with the larger charge, meaning it has less of a chance to penetrate to the spinal cord which is the only truly guaranteed one-shot stop.
.40S&W is a hybrid; it combines the high penetration of 9mm with 50% more bullet mass and a wider hole like the .45. Recoil is somewhere between a 9mm and a .45, as is cartridge size and therefore capacity in a flush-mount magazine. It's a big bullet and therefore doesn't REQUIRE hollow-points to be highly effective like the 9mm, but it has a greater chance than the .45ACP to touch backbone.
.38 Special is a very venerable round; Army pistols of the late 1800s and early 1900s were chambered in .38 variants like Long Colt that gave birth to the .38 Special, and the .38's big brother, the .357 Magnum, is right up there with the .45 in name recognition. .38 is a revolver round, limiting ammo capacity, but .38 "snubbys" are very popular "pocket pistols" for defense purposes when concealed carry of a larger weapon is undesireable or impossible, such as a woman in a dress with a small handbag. It has a bigger charge than a 9mm, but because of the gap between chamber and barrel some of that is wasted. The standard .38 round is unjacketed, meaning even a "ball" round will deform significantly on impact and produce a bigger hole than the barrel bore. The major disadvantages are ammo capacity and cost; .38 rounds are on par with .45ACP ammo, and .357 rounds are even more expensive, and even though the design is very simple, many .38 revolvers are as expensive or more so than autoloading counterparts.
After all that, really it comes down to the biggest round you fire well, in the biggest package you can carry invisibly. I shoot a 9mm because I do not carry; it is a home defense and target pistol, and also my first gun, so cost of the weapon and the ammo was and is important. Others say you can't put a price on your safety and carry the "manstopper" 230-grain .45ACP in a compact 1911. For others, sub-compact "pocket pistols" are the only way to go, opening up .38 as a possibility and limiting the power of high-mass rounds like the .45 as the short barrel limits acceleration. And some want a bit of everything and choose a .40S&W compact. Speaking in terms of being on the other end, I would not want to take a hit from any of the above, making all of them effective against someone who notices and cares that they've been shot. Against a druggie, the object is rapid incapacitation, meaning you're aiming for major blood vessels and blood organs like heart/lungs/liver, and for the central nervous system (head/spine). Penetration is key for central nervous system, while big hole is key for blood-bearing organs. Either way, any of the above rounds will be effective; the key is shooting accurately, and so you want the most powerful round you can control.