I’m planning on doing a series of tests to explore the question of whether and/or how much caliber matters when choosing a firearm, but until then, I wanted to take a moment to explore the bigger question…

Does The Caliber Of Your Gun Matter?  At All?

I have spent an absurd amount of time, and money, and effort, on testing ammo, trying to find what performs best from my various firearms, especially the little guns, and sharing that info for anyone else who may be interested in the same.

And I’ll be the first to tell you — obsessing over caliber and hunting for “magic” bullets is the least important factor in armed self defense. I do consider it a factor, but it pales in comparison to the other more important factors.

There are no reliable statistics out there, that I know of, that assess the question of whether or not the caliber of a gun made a difference in any specific defensive encounter.  Specifically, there’s no comprehensive data on a failed defensive gun use where a medical expert could point out a particular gunshot wound and say “see, if this person had been shot with a .40 or .45, that would have ended the fight right here and now, but because they used a 9mm the perpetrator wasn’t stopped.”  Singular incidents exist, definitely — perhaps the most famous being the 9mm bullet used in the ill-fated 1986 FBI Miami Shootout.  In that case, the 9mm was on a path to hit Platt’s heart, but stopped just an inch short.  Had it hit his heart, it may have incapacitated him much quicker.  That was a clear case where using a different type of bullet may have changed the outcome of the fight, or using a more powerful caliber may have changed the outcome, but — we don’t know that it would have changed the outcome.  And the fact that I had to go back to a case that happened 29 years ago, just to bring up an example, should point out just how huge the lack of data is on this subject.

What Factors Do Matter?

Not all defensive gun uses result in shots fired.  Not all shots that are fired hit the target.  And not all shots that hit the target, do any significant damage.  There are many instances where the caliber of your gun won’t matter at all.  Really.

Here’s how it breaks down, as far as I have been able to ascertain:

1) A large percentage of encounters end as soon as the bad guy sees that you are armed. Merely brandishing your firearm is frequently enough to convince the bad guy to leave you alone.  Exactly what percentage this is, we don’t know and will never know accurately, because many of these encounters are never reported. It’s impossible to gather accurate data if someone won’t share their experience, and if no shots are fired, sometimes folks don’t feel like sharing that story with the police. John Lott has done extensive research and conducted surveys on defensive gun uses, and he estimates that 95% to 98% of defensive gun encounters end with no shots being fired at all; just the sight of a gun causes the bad guy to change his mind and disengage.  There are other surveys out there that put the number lower; I’ve seen estimates of 70% to 80%.  Now, there’s no real way for us to know for absolutely certain what the number really is, so I’m going to take a wild guess at the middle ground and use 90%.  I’m not asserting that this number is accurate, only that it represents the middle ground between the high and low end of surveys that have been taken, and because no hard data actually exists, we cannot truly know what the true number is anyway.  So, for purposes of continuing the discussion, I’m going with 90%.  If we use this 90% figure, we could conclude that in at least 90% of defensive encounters, caliber doesn’t matter at all and makes no difference in the outcome of the encounter.  The bad guy turned and ran whether the crime victim was using a .22lr mini-revolver or a .44 Magnum.  Just the sight of a gun was enough to end the encounter.  Heck, odds are pretty good that the gun wouldn’t even have needed to have been loaded!

2) For the remaining 10% of encounters, the crime victim needed to do more than just show that s/he had a gun.  This means the trigger was pulled and  a shot was fired.  Now, presuming that a shot was fired towards the bad guy, we know that some percentage of those encounters will end immediately whether the bad guy is hit or not. As far as I know, we have no way of knowing what that percentage is, but surely there is some percentage of the bad-guy population who, when faced with the sight of their intended victim brandishing a gun, might think “oh, that’s not a real gun” or “no way this guy will have the guts to actually shoot me” or whatever.  For whatever reason, the sight of a gun is not enough to deter this particular crop of bad guys, and they may continue to attack — right up until their intended victim pulls the trigger. At that point, some percentage of the bad guys will turn tail and run, even if they weren’t hit.  Now, what percentage of bad guys will see a gun, but continue to try to mug/rob/rape/kidnap/etc you anyway, but will turn tail and flee when that gun gets fired? I have no earthly idea.  I haven’t seen any data on this, I haven’t seen any studies that have broken it down to this degree.  Simply put, I have no idea at all.  I just presume that it is logical and reasonable to think that there must be some percentage of bad guys who are dissuaded by the flash and noise of a gunshot, and will disengage because of it.  But there is no data (that I know of).  So, even though I am loathe to do it, I am left with no choice: I simply must make a random number up off the top of my head.  Let’s go with 1/3. Now, I have no idea whatsoever if that’s right, or close, or wildly wrong. I just know that we need some sort of number in order to continue exploring this question, and — even if this number is wildly wrong, I think you’ll see by the final conclusion that it really doesn’t matter all that much.  This final conclusion won’t and can’t be a a proper scientific conclusion because we simply do not have the data to go off of, so — we’re taking wild guesses here. So, in this hypothetical, wild-guess narrative, maybe 1/3 of the bad guys who didn’t flee at the sight of a gun, would indeed turn and flee when someone takes a shot at them, even if that shot misses. Which, for purposes of this discussion, means (once again) caliber doesn’t matter in these scenarios.

Adding together the 90% of bad guys who disengaged at the sight of a gun, with the 3.3% (1/3 of the remaining 10%) who were dispelled at the sight and sound of the trigger being pulled, that puts us at 93.3% of potential defensive gun uses ending with caliber not mattering at all (even though, again, these numbers bear no basis in reality, because we cannot know the true statistics, because they are not reported).

3)  That brings us to the third class of encounters — ones where the bad guy actually gets shot. Now, in our (admittedly inaccurate) tally here, only 6.7% of armed encounters are going to get this far, because in the other 93.3%, no shot needed to be fired. So what happens when a bad guy gets shot, by ANY bullet, of ANY caliber, whether it’s a hollowpoint or a frangible or an FMJ, whether it’s from a .500 S&W or a .22LR or something in-between? According to my evaluation of Greg Ellifritz’s “An Alternate Look at Handgun Stopping Power“, the numbers are pretty consistent — approximately 60% of people who get shot, give up immediately.  According to Ellifritz’s data, approximately 60% of the encounters ended with one shot being fired, almost regardless of what handgun was used.  It doesn’t matter whether it’s 9mm or .357 Magnum or .40 S&W or 10mm or .44 Magnum or .22LR; the numbers were always in the general ballpark of 60% (ranging from 47% for the 9mm, up to 72% for the .32 ACP, but most calibers came in between 51 and 62%).  It doesn’t matter if the bullet was a hollowpoint or an FMJ or a frangible.  People apparently don’t like getting shot.  Apparently it doesn’t feel good and apparently it’s enough of a shock that they just plain stop right then and there. Now, what we DON’T know, from the data, is how they stop — whether those approximately 60% all drop dead from that one shot, or they faint, or they turn tail and run, or they calmly walk away, or if they put their hands up. Certainly some of this 60% of shooting incidents included all of the above. The data we have doesn’t discern among them. We don’t know WHY they stopped, we just know that they did stop. Updating our statistics, and using 60% as the approximate number of people who were discouraged or forced to stop after a single hit, that means that of the 6.7% of bad guys who actually needed to be shot to stop, 60% of them stopped after one bullet of any kind, so that’s 4.02%. If we add that 4.02% to our prior 93.3%, we’re up to 97.32% of armed defensive encounters where caliber basically did not matter and did not make a difference.

That leaves 2.68% of the encounters where caliber may or may not make a difference.

Stunning, isn’t it?  And, yeah, my numbers may be off — in fact, I guarantee they’re off.  But how far off do they need to be, before it starts to make a difference?  If we used John Lott’s assessment that 98% of encounters ended just by brandishing a weapon, then (keeping all our other numbers the same) that would mean caliber didn’t matter 99.53% of the time.  Or, taking the low end of the estimates (that 70% of encounters ended by brandishing), that would mean caliber didn’t matter 92% of the time.  So, take your pick — caliber mattered either 8% of the time, or 2.68%, or 0.47%.  Whichever you go with, I’m sure you can see we’re basically picking nits at this point.  I’m reasonably comfortable with my middle-of-the pack estimate  of 90%, and that leaves us with 2.68% of the incidents where the caliber of the gun might matter.  But in any of the described scenarios, it should be obvious that the caliber of the gun is not the most important factor when discussing a successful defensive gun encounter.

So let’s look further into those shooting scenarios where caliber may have mattered (meaning, in those 2.68% of encounters, the person didn’t stop just because they were shot with some bullet somewhere in their body, they continued their attack, and needed to be shot multiple times to force them to stop.)  How do we determine whether the caliber mattered or not? Once again, there’s no real way to know.  A person shot with a .22LR through the brain stem will drop instantly; one shot through the thigh with a .45 ACP FMJ may not even show any reaction.  Or they might — they might faint right away.  Here’s the tricky thing: even though we know (from Ellifritz’s data) that there were people who stopped after being shot multiple times, we don’t even know whether or not multiple shots were necessary.  Maybe the first shot was a .22 that hit them in the thigh and didn’t force them to stop, but the second shot went through the brain stem and dropped them immediately. Or, maybe they were shot 21 times by a .40 S&W and wouldn’t stop, and the 22nd shot they were hit with went through their brain and forced them to stop (it’s happened before). Or maybe they were hit with a quick double-tap — maybe they would have stopped after being shot just once, but the good guy hit them with a second shot so quickly that the bad guy didn’t have a chance to stop before being hit with the second bullet.  This might be the case in many police shootings, where multiple officers might unload on a suspect simultaneously — perhaps the suspect would have quit after the first hit, but we can’t know because he was hit with multiple shots before even getting the chance to stop. We don’t know, the data doesn’t specify.  It’s entirely possible that the earlier estimate of about 60% (of people stopping after being shot once, regardless of caliber) is low, because perhaps some percentage of multiple-shot scenarios would have ended after the first shot.

What we do know is that for this last 2.68% of defensive encounters, we’re probably past the point of wondering whether our super-duper-magic-frangible bullet had enough mystical “stopping power”, and we’re into the category of “the bullet had better damage the bad guy’s body enough that they cannot continue to threaten you.” And here’s where we really need to focus on shot placement first, and caliber second.

Shots That Will End A Gunfight

A perfectly placed shot on the central nervous system (one that hits the upper spine or brain stem, or through the major circulatory system organs) WILL, without a doubt, bring a fight to an immediate stop, guaranteed (but if, and only if, the bullet has sufficient power to reach and destroy those organs). If your ammo falls short, there’s nothing that your shot placement can do to make up for that, but as long as your ammo penetrates deep enough to hit those targets, shot placement on those areas will result in an immediate cessation of hostilities.  No human being can continue to attack you if a bullet has damaged their brain stem or upper spinal column.

Additionally, a perfectly placed shot on the major circulatory system organs will absolutely bring the fight to a stop, in short order but not necessarily immediately.  If a bullet damages a major circulatory system organ (such as the heart, or a major artery), blood loss will, sooner or later, cause the bad guy to drop unconscious.  However, once again, the bullet needs to penetrate deep enough to do its job.  A perfectly placed shot that stops 3″ under the skin will likely not force a stop. A deep-penetrating bullet that misses the vital organs and only zings through a shoulder or thigh, will likely not guarantee a stop. A .22LR or 9mm FMJ through the brain may or may not cause a stop. A 9mm JHP through the heart will cause a stop — maybe not instantly, but within a dozen seconds or so the bad guy absolutely will stop, as blood loss causes them to lose consciousness — and in this case, a .45 hollowpoint will probably bring about unconsciousness faster than a .22LR roundnose, even though both would likely eventually cause unconsciousness; bigger holes will result in faster bleedout and a more rapid loss of blood pressure. Shot placement matters a lot, and bullet performance matters, but amazingly enough they only really seem to matter in this last group of 2.68%.

Now, truth be told, the data is inconclusive and unreliable. We don’t know that the group is really 2.68% (even if we assume that the 90% figure for no-shots-fired is accurate, or the 1/3 wild guess for shots-fired-but-missed is accurate). In that last 2.68%, all we know is that they weren’t stopped by being hit by only one shot. What we can’t know is whether they may have chosen to stop after two, or three, or four shots — even if none of those shots were true incapacitating shots! There may be a tough guy out there who takes a 9mm to the shoulder and shrugs it off, but after three or four of them he may decide to throw in the towel. What % of bad guys would this involve? No way of knowing, other than to say it seems reasonable to assume that there is SOME % of them out there.

Here’s the thing — will YOUR defensive gun use be part of that first 90%? Or will it be part of that last 2.68%? I don’t know. You don’t know. Caliber may be irrelevant in your situation — or it may matter. It might. We just don’t know.

Wrapping It Up

After years of studying this subject, these are my conclusions: in a majority or even potentially the vast majority of potential encounters, caliber will not matter. But sometimes it might. And sometimes, it will. What kind of encounter will YOUR defensive encounter be? The odds say caliber won’t matter, but the reality says that if it’s MY life on the line, I want the best chance of surviving I can get. And that’s why I’ve spent so much time testing ammo from a wide variety of guns: because I cannot control what type of bad guy I will encounter, I cannot pick and choose what scenarios will cause him to flee or stop, but I CAN control what goes in my gun, to at least verify that IF I end up in the worst-case scenario, at least I know that my ammo will be capable of doing the job that needs to be done.

Better shot placement can take years of training and effort and, sometimes, luck. Better ammo performance? That’s a matter of just spending $20 and picking up the right box of ammo for the type of gun you’re using. You may or may not be able to control your shot placement, but you definitely can control your ammo choice. In the end it may or may not matter, but if you encounter one of the rare instances where it does matter, then — seems like such an easy thing to fix, why not use stuff that performs properly and gives you that little extra edge?  And that’s why I test for deep-penetrating, proper-performing hollowpoints from even the smallest of pocket guns.

We also know that there’s such a thing as physics.  Larger bullets lead to larger holes.  A smaller bullet (like a 9mm) can be made to expand to a larger size, but there’s always a chance that an expanding bullet might not expand.  It happens.  As fans of the .45 say, a 9mm might expand, but a .45 will never shrink.  Also, bigger bullets can carry more momentum and smash through bigger bones and stay on course better, but that’s not to say that smaller bullets can’t get the job done satisfactorily.  Smaller bullets (9mm for example) can give you greater capacity in your magazine than larger bullets (.45 ACP for example) will — and that may mean you have more chances to put shots on target before the gun runs dry.  These are some of the things that we do know.  But how important are these factors, in the overall scheme of things?  It seems like in 97.32% of the cases, not important at all.  But in 2.68% of the cases, it may matter some.  I doubt it will ever matter a lot.  To what degree it does matter, that’s why I carry a .45 or 10mm whenever possible. Even though I know it won’t matter most of the time, I cannot predict when it will matter, and I want to be as prepared as I can be.  As has often been said, nobody who’s ever been in a gunfight has ever said “man, I wish I’d brought a smaller gun.”

But knowing how little it’s likely to matter, that’s why I also feel plenty adequately armed with even a 9mm pocket pistol, and why I have on occasion carried only a pocket .380.  Because in somewhere around 97% of the potential scenarios that I’ve been able to identify, caliber doesn’t seem to matter.  Being armed, however, does seem to matter very much.  Remember, depending on the estimates you use, between 92% and 99.5% of all defensive gun confrontations were settled just by having been armed at all.  Given those numbers, it seems prudent to reiterate Rule 1 of Gunfighting: Have A Gun.

My advice: carry the biggest, most powerful firearm that you can comfortably conceal and accurately shoot.  If, for you, that means a 10mm, then you will be well prepared to meet any threat that a handgun can be expected to meet.  If, for you, all you can handle is a pocket .380, then go for it — you’ll still be prepared to handle a huge majority of potential defensive gun encounters (if the data is to be believed).  Don’t use this article as justification to carry less gun than you know you should, but do take from it that the first and second priorities are that you should be armed, and that you should be skilled with your firearm.  Everything else (caliber, capacity, particular ammo, draw speed, etc) pales in importance with those first two priorities.  They’re still important, but don’t ignore the bigger picture by getting caught up in the minutia.