What Caliber/Size Semi-Auto for Home Defense


So you’d prefer a semi-auto for home defense?

While we said on the matching page to this one, for people choosing a revolver for home defense, that we’d not second guess them, in truth a revolver is not our first choice for home defense.  So congratulations on choosing a semi-auto.  For most people, it is probably the best choice.

Now let’s lightly touch on the two main remaining options open to you.  The caliber and size of semi-auto.

The good news is that you don’t have to worry about size limitations at all.  The gun will probably live somewhere in your bedroom nearly all its entire life, and if you ever need to use it, for real, you’ll hopefully only need to pick it up and carry it only a few feet to your safe area while you wait for the police to show and ‘do the heavy lifting’.

So there’s no need to choose something small and light and concealable.  Instead, you can choose as powerful a caliber as you’re comfortable with, and as large a weapon as you can conveniently grasp and fire.

Caliber Choices

For a home defense pistol, we recommend the caliber you should choose is 9mm.  You should also think about two other common calibers – .40 S&W and .45 ACP.

There is no reason to consider smaller and less powerful calibers, which are only appropriate (if ever) in situations where you need a very teeny tiny pistol that is ultra-concealable.

The 9mm caliber is the least powerful and the smallest of the three.  On the positive side, it is the most controllable (because of its lower power), and ammunition is close to universally available, and at considerably lower prices than for the other two calibers.

At the other extreme is the .45 ACP round.  Both it and the 9mm round date back over 100 years (the .40 S&W is relatively modern, having been introduced in 1990).

The .45 ACP is a big heavy and moderately slow bullet, made famous by the M1911A1 semi-auto pistol.

After its adoption by the FBI in the early 1990s, the .40 S&W cartridge gradually became the cartridge of choice for many law enforcement agencies, and for many civilians too.  It is smaller than the .45 which allows a gun to be smaller and to hold more rounds in its magazine, but has very similar (or even more) energy and a faster, albeit slightly smaller bullet.

But the FBI had a change of heart a few years back (about 2014) and switched back to the 9mm, and again, their choice is being copied by other agencies and by the civilian population too.  The reality of the .40 round is that it gave a lot more felt recoil than either the 9mm or the .45, making it less easy to shoot well and less easy to shoot quickly.  The popularity and sales of pistols chambered for the .40 cartridge is plunging.

There are many other calibers available too, but none of them are at all common compared to the ‘big three’ of 9MM, .40 and .45.

That’s not to say these other calibers are ‘bad’, and indeed one of our own favorite pistols is an FN 57 that shoots a decidedly unusual caliber – 5.7x28mm.  But most of the time, most of us will have all our needs perfectly well met by a regular mainstream caliber.

If nothing else, choosing a mainstream caliber means you can get a competitively priced, well-tried and true pistol, and have a choice of different ammunition to go with it from different suppliers, also competitively priced.  (In comparison, there is only one pistol in the world that shoots 5.7x28mm ammunition, and only one regular manufacturer of the ammunition, too.  Unsurprisingly, both the pistol and the ammo is more expensive than is the case with regular guns and ammo.)

Unless you must have an M1911A1 type pistol, we suggest you choose a pistol chambered for 9mm.  While some people will claim the .45 round is a ‘better’ round (in the sense of requiring fewer shots to stop an attacker) the ‘science’ behind those claims are problematic, and if you look at the two rounds side by side, the extra diameter of the .45 cal round is not much more.  If the FBI have deemed the 9mm the best round, that’s good enough for us, and should be good enough for you, too.

Gun Size and Capacity

You should now be at the point where you’ve chosen the ideal caliber for your home defense semi-auto pistol.  Now to choose the gun to fire that caliber of cartridge through.

You’ll see a huge range of different semi-auto pistols in the caliber you’ve chosen, ranging from tiny little things up to huge big heavy monsters.

Get the biggest gun you can comfortably hold and grip and shoot.  The bigger the gun, the less the recoil, and the longer the barrel, the more accurate the shots and the less the muzzle blast/flash.

In terms of size, you want to be able to wrap your firing hand (probably your right hand) reasonably around the grip and have your firing finger (index or trigger finger) able to curve around comfortably, with it resting on the trigger somewhere between half and two-thirds the way down the first segment of the finger.

Bigger guns also probably have larger capacity magazines, too.  While hopefully you’ll never need to shoot your gun in anger at all, and if you ever do, hopefully you’ll only need to shoot it once or twice, the whole concept of a gun is to be prepared for the worst case scenario, not the best case scenario, so the greater the capacity of the gun, the better.

Whatever you choose should hold at least 13 rounds in its magazine, and better if it holds 15 or 17 (or even more).

Bigger guns may possibly be slightly more reliable than smaller guns, because the designers don’t have to make compromises or save weight.  On the other hand, at home, the best reliability guarantee is to have a spare pistol right next to your first one.  It is also the fastest way of ‘reloading’, too – to simply drop your first pistol and pick up your second (this is called a ‘New York reload’ in popular parlance).

Extra Features

The mounting rail on a Glock 17 Gen 4

Some people wish to mount a flashlight and/or laser sight to the gun.  We’re a bit ambivalent about that, but will discuss it in a separate article.  If you want to at least have the capability to mount such things,  you want a pistol with a mounting rail (usually a ‘Picatinny’ rail).

This, which is typically on a pistol’s ‘dust cover’ (see picture, left) allows a range of different devices to be mounted.

You could also consider adding some type of optical or night sight to the pistol as well.  Because you’re not going to be carrying the pistol, nor needing to conceal it, some of these slightly fragile and definitely bulky extra accessories can be considered, and with the probability that any encounter you’ll have will be in low light or no light, it is acceptable to consider having some gun mounted rather than free-standing devices.

And So?  Your Choice Is?

Have you made a choice yet?  You’re doing well.  You’ve almost identified the semi-auto that is best for you.

Please now move on to the page ‘Buying a Semi-Auto for Home Defense Summary’.  Or, if you’d like to return to the first page of this guide to choosing a pistol, please click the link in this sentence.


  One Response to “What Caliber/Size Semi-Auto for Home Defense”

  1. I was enjoy your articles about home defense firearms but I could find the one titled: ‘Buying a Semi-Auto for Home Defense Summary’. Could you please send me a link?
    Thank you,
    Joel Wier

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