Well, you’d be right. Between a .45 ACP and a 9mm, there’s no clearly defined winner, but when it comes to home defense specifically, the 9mm has a slight edge in our humble opinion.
Let’s talk about the .45 ACP first.
The .45 ACP is a larger, fatter, more powerful caliber of bullet. Because of its higher weight, it has generally better stopping power than the 9mm. Each bullet is larger, which makes the firearms that use the .45 ACPs larger as well (compare the 9mm Glock 17 with the .45 ACP Glock 21 and you’ll see). Now, larger doesn’t always mean worse, but a smaller yet still full-sized gun (like the Glock 17 or even 19) can generally be used by a greater number of people than a larger handgun can. They are also easier to conceal or stash in a not-so-obvious place (the dimensions of some biometric safes—the fastest safes to open and get your self-defense gun—might not accommodate a large .45). Finally, you’re not likely to need the kind of firepower the .45 ACP provides when you’re defending your home. You’re likely to be in close enough quarters with the perpetrator where a 9mm is more than sufficient.
Another thing to consider about the .45 ACP is the recoil.
With great stopping power comes a greater recoil. If you’re used to larger caliber firearms, this may not bother you much at all. You’ll still notice it, but you may not be physically impacted negatively. However, your accuracy will almost certainly be impacted by the recoil. There’s a little math involved in determining the course variance of your bullet based on how much the barrel moves when you shoot, but I won’t bore you with all that. Just believe me when I say that the bullet will not be as accurate with a higher recoil weapon, which is not something you probably want when you’re firing in an enclosed space, possibly in the dark.
Look, there’s a reason law enforcement use 9mm or are returning to it after years of using the .40S&W—the 9mm’s a darling of a round. It’s very commonly available and tend to not be exorbitantly expensive. Cost issues aside, we return to the 9mm’s general lack of recoil when you fire. Yet, despite this smaller recoil, we’ve likely all heard the stories of the damage a 9mm can do (a lot of police shootings were enacted with a 9mm sidearm) and the news is a testament to the fact that a 9mm is more than capable of helping you defend your home, especially when you use modern hollowpoints like Winchester Rangers or Federal HST’s.
If you’re still unsure about which caliber is right for you, take a look at some of the research the US Marine Corps published on .45 ACPs vs. 9mm and why they will use 9mm for their operatives, or go try out both calibers yourself before purchasing one. The recommendation is still the 9mm, but sometimes it’s helpful to experience both rounds for yourself. When you’re firing both, consider the size of the firearm, the grip, the recoil, and what it does to a target set at 10 yards away, which is still likely a greater distance than you would shoot in a home defense situation.
And we can’t get away from the cost issue.
Yes, there’s an ammunition shortage right now (writing this mid-2021) so everything is expensive, but whatever the time, the .45 ACP round is going to be always more expensive than the 9mm Parabellum. In other words, not only can you shoot and practice more with the 9mm than the .45 ACP, but those high-tech hollowpoint wonder rounds (like, say, the aforementioned Federal HST’s) are going to be more expensive too. And what is the purpose of buying more expensive bullets when you can buy them cheaper? So you can say you use .45 ACP’s instead of 9mm? Doesn’t make a lot of sense. Besides, .45 ACP’s make the most sense in 1911’s anyway, and 1911’s, while marvels of engineering and ergonomics, aren’t known to be the most reliable of handguns. Needless to say, you’ll want maximum reliability in a home-defense gun and shooting a 9mm from a Glock or, even better, an all-steel handgun like a Beretta 92 will likely give you the maximum reliability of any semi-auto gun out there (revolvers are more reliable, but that’s for another article).
Also, let’s talk about capacity—you can have more 9mm bullets in your gun than a .45 handgun, all other things being equal. I return to the Glock 21 vs the Glock 17. The former, shooting .45ACP, holds 13 while the 9mm-shooting Glock 17 holds 17—with optional magazines that can even hold 33 rounds! Which brings up another aspect: firing the 9mm means you’re using the most popular centerfire round in the world with just a greater plethora of upgrades and parts you can buy (like those aforementioned 33-round Glock original magazines).
At the end of the day, the caliber of ammunition and the weapon you choose for your home defense will all depend on your priorities, your comfort with firearms, and the environment you anticipate using the firearm in. The 9mm is a good all-purpose weapon, but you may find that you prefer the feeling of the .45 ACP, despite everything we’ve gone over in this article. It’s a personal choice and testing each caliber at least once is a good bet before you decide what’s best. It’s always good to be armed with the facts, so now you have a little insider information into the difference between the 9mm and the .45 ACP. Try the 9mm first and consider the pros and cons before moving on to the .45 ACP. Good luck!