People who are new to handguns and defensive shooting may be somewhat surprised at the fervor that is exhibited during debates about the various defensive handgun calibers. The 9mm vs. .45ACP debate has been going on for years. And I am sure that this makes the .40 S&W and 10mm advocates feel discriminated against and inclined to add to the furor of debate. It occurs to me that all of these caliber wars may be more than a little bit confusing to new folks. So, making a concerted effort to keep from taking sides, let me see if I can explain what all the argument is about.
We use our defensive handgun only when our lives are in immediate danger. Our goal is to stop the criminal's attack immediately, before he can do any damage. This use of our defensive handgun may cause the death of our attacker, but his death is not our goal. What we want is for him to stop his attack immediately. Significant tissue damage is the only thing that can be relied upon to cause the incapacitation of the bad guy.
The 9mm cartridge is a stalwart for the Small & Fast fraternity. It pushes a 124-gr. bullet (.358 inches in diameter) in the neighborhood of 1150 feet per second (fps). This relatively high velocity can be expected to give a modern hollowpoint bullet some 15 to 17 inches of penetration into the bad guy. At the same time, these modern bullets will expand. It is this combination of penetration and expansion that is relied upon for incapacitation.
Most 9mm advocates will admit that 9mm ammo using a full-metal jacketed bullet is not a good fight stopper because, while it has velocity, it doesn't have the ability to expand. They point, and rightly so, to the huge improvements in the design of defensive handgun bullets within the past few years. We simply know a lot more about how to manufacture a proper defensive handgun bullet these days, and the 9mm has benefited from this technology.
The best example of the Big & Slow class is the .45 ACP cartridge. Traditionally, the .45 ACP has pushed a 230-gr. (.452 inches in diameter) bullet at some 850fps. While the .45 bullet is not traveling as fast as the 9mm, it relies on increased bullet weight to give the needed penetration.
The .45 ACP cartridge began life with a full-metal jacket bullet, must like the 9mm. However, the .45 FMJ bullet has a little better reputation as a fight stopper, undoubtedly because of its weight advantage. And, as with all defensive handgun calibers, the .45 ACP has benefited from the improved design of modern defensive bullets.
So one may wonder why there is this on-going debate when both the 9mm and the .45ACP penetrate sufficiently and, especially with modern ammo, expand sufficiently. They both should be able to cause significant tissue damage and result in rapid incapacitation of the attacker.
Well, to confuse things even further, they are both capable of a failing at this task, too, and have on documented occasions. Think of all of the things that the defensive bullet might have to go through in order to impact the criminal. Glass, sheetrock, heavy clothing...these may not only slow down the bullet, reducing penetration, but they might clog up the hollowpoint and cause it to fail to expand.
One might come to the realization that caliber is not as important as finding a defensive handgun that is easy to operate and easy to shoot well. Once that is determined, one's time might be better spent researching the best defensive ammunition that is available and acquiring the same. After that, the smart thing is to get professional defensive training to learn proper tactics and proper bullet placement.
You will notice that I haven't taken sides in the Small & Fast vs. Big & Slow debate. I suppose some people are welcome to continue this debate ad nauseum. As for me, I think I'll go spend the afternoon at the shooting range, trying to get as good as I can with my chosen defense gun.