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Few topics are as hotly debated as the question of “which caliber”. This article addresses my thoughts on the topic for semi-automatic (autoloading) pistols, intended for self defense use.

While bullets of every caliber are deadly if placed correctly, some are more effective than others. For example, a .22 caliber bullet is a deadly thing worthy of respect, but I would not want to trust my life to a .22 bullet during a home invasion. Similarly, a .50 Action Express is a devastatingly effective round as far as handguns go - but the large size of the cartridge and significant recoil make it less effective overall, compared to other cartridges. Below is a list of commonly available pistol cartridges, and my opinion as to their desirability for self defense, in the order which I prefer them.

1. .40 S&W
The .40 Smith and Wesson is my favorite defensive pistol caliber. It is almost 2 decades old, yet has become very popular in the USA. With 135 grain bullets, it delivers energy levels matching or exceeding standard .45 ACP cartridges, but in a smaller form factor that allows for subcompact handguns. Fans of the .45 ACP will point out that the bullet diameter of the .40 S&W is 0.05 inches smaller, but given the excellent expansion performance that can be expected from modern hollow point bullets, I’m not concerned by this at all. The higher velocities of .40 S&W bullets (up to 1325 feet per second) compared to the velocities of .45 ACP (around 900 feet per second) also help ensure that the hollow point bullets will expand as they are designed to.
Recoil is brisk due to the higher velocity of the bullets, since the recoil energy is transferred to the shooter’s hands more abruptly than with lower velocity cartridges, but the recoil is not overwhelming. I have found the recoil in pistols chambered for .40 S&W to be subjectively slightly higher than that experienced in comparable pistols chambered for .45 ACP. I have also found that even those adverse to recoil can become accustomed to a Springfield XD chambered for .40 S&W after firing just a couple hundred rounds.

2. .45 ACP
The .45 Automatic Colt Pistol cartridge has been around for nearly a century, and has proven itself an effective self defense caliber. That said, it is not a magic caliber that will banish a dozen home invaders from your house in a single bound. This cartridge fires a relatively heavy bullet at relatively low speeds, which is effective, but does not take advantage of the way a slightly lighter bullet at higher speeds can be more effective, carry more energy, and recoil more softly. Part of the reason for this is the lower chamber pressure, compared to more recently introduced cartridges. For that reason, this time tested and effective caliber is my number 2 choice for self defense.

3. .45 GAP
The .45 Glock Automatic Pistol cartridge is less than a decade old, and was introduced by Glock as a way to fit a .45 caliber bullet into the frame of a compact pistol, where the .45 ACP would not fit. The result is a cartridge that is shorter in length, and has a higher chamber pressure than the .45 ACP. Performance is similar to the .45 ACP as well, however the price tends to run about 10% - 15% higher than .45 ACP rounds. This cartridge is also less common, and its future is not as secure as that of the .45 ACP that has been around since before my grandparents were born (although I have yet to visit a gun store that didn’t have .45 GAP in stock).

4. 9MM
The 9×19MM Parabellum cartridge, like the .45 ACP, has been around since before World War 1. It is a round that originated in Europe, for the Luger pistol, which is why it is measured in millimeters, rather than fractions of an inch. The bullet diameter is the equivalent to .35 caliber. It is about the minimum caliber I would recommend for self defense, except in for people who are too recoil sensitive to handle even a 9MM pistol (which is rare, and can often be overcome with just a little practice).

5. .357 Sig
The .357 Sig is is a relatively new, and designed to match the performance of the well respected .357 magnum, but in a cartridge designed for semi-automatic pistols rather than revolvers. It almost lives up to this goal, packing more energy than a .40 S&W or .45 ACP, when 115 grain bullets are used, but falling short on heavier bullets. The 35 caliber bullets it fires can be effective, however I feel that for self defense, the .40 S&W and .45 ACP cartridges’ larger diameter bullets are more effective and less prone to over penetration. The 9MM is less prone to over penetration than the .357 Sig.

6. .32 ACP
The .32 Automatic Colt Pistol cartridge was introduced in 1899 for use in small, self defense pistols. While like all cartridges it can be deadly, I am reluctant to recommend it to anyone except those who really can’t handle the recoil from a 9MM or larger caliber pistol, which is very few people. Having a self defense handgun chambered for .32 ACP sure beats throwing rocks or brandishing a pointy stick, but its ability to stop attackers is considerably lower than the above calibers.

In this article I don’t discuss a variety of cartridges. Not because they are bad, but because I don’t believe that they are generally ideal for self defense. For example, the .22 LR and .25 ACP are generally too small and too under powered to reliably stop an attacker. Other less common cartridges are not included either.

Other cartridges, such as the .50 Action Express, which the Desert Eagle fires, generate tremendous recoil that can reduce the speed and accuracy of follow up shots. Two well placed .40 S&W bullets will do better to stop an attacker than one poorly placed .50 AE bullet [Although the Desert Eagle is a fine firearm ]. Also, the large size of these cartridges means that the guns chambered for them will have a lower magazine capacity. Those extra bullets can be the difference between life and death.

It is also important to remember that few firearms issues are as contested as the “which pistol caliber” question. Some people swear by .45 ACP. Others, like me, prefer .40 S&W. Many people like 9MM, while others believe the .45 GAP is the best thing since sliced bread. Regardless of which caliber you choose, the most important thing is to get a gun that you like, and to shoot it often. An inexperienced shooter, with any caliber, will not be anywhere near as able to defend themselves as an experienced shooter with even a less-than-desirable caliber.

This article addresses home defense handgun accessories you may want to consider as well.

If you are unsure which type of gun to select for home defense, this article may help.