Does caliber really matter?

I cary a Glock 42 (380) every day and am considering going to a Glock 43 (9mm) or a .38 spl revolver. I have always thought that caliber really wasn’t a big factor in a self defense situation as long as you were competent enough to put three quick shots center mass. After watching some of the training videos, I’m not so sure I am correct in this assumption. I would welcome any input from the community on this subject.


A modern .380 defense round can almost equal a low end 9mm.

A .380 though is never going to give you the same energy and penetration as the 9mm using equally “hot” loads.

The .380 is ideal where over penetration is a serious consideration but you can count on probably having to put several more rounds into the torso to get the desired effect vs a similarly loaded 9mm.


It’s a trade off. A .380 and a 9mm in similar sized guns, the .380 will be more “shootable.” I don’t want to get shot with a .380. That said, during winter, when the attacker might have on thicker, heavier clothing is when the 9 shines over the .380. More penetration becomes a plus then. Some modern ammo(Extreme Penetrators) have helped that issue. Make sure they will work in your gun. I’m a big proponent of carrying the biggest gun, in the biggest reasonable caliber that YOU can handle. No one will ever wish they had a smaller gun if they ever have to use it.

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I believe that caliber wise, no. Your ability to shoot well, and get your hits is more important. If you can shoot a 9 as effectively as a .380, then yes, I believe you would be better off with the 9. I believe a .38 with a good +P load would also be better than the .380. Although I am not a revolver person, just from what I have read.


I believe you should carry the most effective caliber you shoot the best. You’re going to have the most confidence with that gun and that means you’ll actually carry it.

The old adage of a 22 in your pocket is better than 45 in the safe.


Not that I haven’t mentioned it before but the 60gr JHP .22 magnum is the most underrated and unappreciated SD round on the market.

If I were having difficulty managing recoil with bigger rounds I’d certainly turn to it.


Without getting into all of the boring math, I look at it this way. Caliber only determines the size of the hole in the target. The mass of the bullet and its velocity when it hits the target is everything. Let me oversimplify. For all intent and purposes, the bullet coming out of my AR is a 22 caliber. It doesn’t make that big of a hole. What makes it especially effective is that it comes out of the muzzle wicked fast.


Since knockdown power has been disproven by the FBI in their switch back to 9mm, the best caliber is one you can control easily and make good hits. Most people lose the will to fight when their bodies start leaking the red stuff. My summer carry is a .380 for light clothes and less printing. My carry for the rest of the year is a 9mm. I train with both weapons to be able to control them easily.

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This is really a multi faceted issue.

Mass & velocity is the key to an effective round, too much of one or the other and the effect is diminished, that’s the pure science part.

The subjective part is recoil, a big round in a “concealed carry” size pistol is going to kick, a smaller round in a smaller pistol not so much.

Conceal ability is the third part of the stool, if it’s too big you can’t conceal it (you may be able to but it’s heavy) but if it’s too small you don’t get round selection.

I’ll add one more leg to the stool that isn’t often discussed, hand size. I have meat hooks for hands, I liked the sub compact XD in 9mm, it was small, light and I could shoot it accurately but the grip kicked my butt on the range, it was too small and bounced around in my hand requiring re-grip often.

In my case I’m stuck with my 1911 Officers model in .45 but I am seriously considering a first Gen XD service model in 40S&W if I can find the right one.



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This is really good information. The advice you get from the community alone is well worth the price of membership. In my original post I did not mention that I am getting older, 73 on my next birthday, and have slowed down and lost much of the strength I had 25 years ago. I like my Glock 42 and am going to stick with it because it fits my hand nicely, I find easy to control and I can get some tight groupings out to about 15 yards. Like my mama used to say “If it ain’t broke, don’t fix it”. Thanks again to the community for a really good conversation and some great advise.


And for some testing reading…

An interesting read which shows that rounds of many calibers may have similar penetration and expansion.

So, shoot a caliber you shoot well, with a round that has good penetration and expansion.

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I agree. That article from LuckyGunner is very informative, and it helped me choose my carry ammo.

Three shots center mass may not work. With any ammo caliber. After all body armpit is for sale everywhere. Pelvis and headshots usually stop the assault quickly.

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Body “armpit” or “body armor”?

The chances of running into a bad guy wearing body armor are astronomically slim and if you do, odds are it’ll be extremely obvious as they’ll probably be wearing a plate carrier.

If you happen to run into same, shoot where the armor isn’t covering them.

Between the top of the plate an bridge of the nose will certainly do the trick.

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Practice a modified Mozambique using pelvis and head shots.

Well well on average it matters greatly depends on your skill set and accuracy in a stressful situation most people even well-trained make pour shots so caliber does matter but you do not want to oversized because then you lose control

The clear answer is a 454 Casull or maybe a S&W 500: everything else is just compromising! (Kidding!)

380+ is usually considered a starting point for self-defense ammo. But do your research on the best bullets and loads that you can. Watch penetration, expansion statistics, etc. Lots to look at!

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