The Statistics Of Stopping Power

The Statistics Of Stopping Power

It is a slow week, and a week of Thanks, so let’s spend our time with some fun things.

Like a fascinating study by Greg Ellifritz on “An Alternate Look at Handgun Stopping Power“. (There are more than just his: this post is mainly for fun.)

“Stopping power” is a somewhat vague term, which doesn’t stop ceaseless claims of this or that round having superior “stopping power.” What makes Ellifritz’s examination worthy is that he quantifies its definition across several dimensions.

Except for one. Which is entirely caliber independent. I mean those times when a mere gun reveal is sufficient to discourage your enemy and he leaves off. I’ve seen varying statistics on this, but it’s not a small number. And to an extent unknown, of course, because most of these confrontations would never be reported, and so no data is ever collected on them.

Which only means, for us, that Ellifritz’s study is conditional on those times in which a firearm was fired. His numbers are therefore a global underestimate of overall stopping power. According to Ellifritz:

Over a 10-year period, I kept track of stopping power results from every shooting I could find. I talked to the participants of gunfights, read police reports, attended autopsies, and scoured the newspapers, magazines, and Internet for any reliable accounts of what happened to the human body when it was shot…

Every shot in this study took place during a military battle or an altercation with a criminal.

He cataloged number of people shot at, number of shots, number of hits, number of fatalities, accuracy, and, my favorite, one-shot-stop percentage, which means just what it says. He had about 1,800 incidents.

Now this data has been played with in many places, and I won’t be able to milk much more out of than others already have. Except to point out the strengths and weaknesses of any kind of statistical modeling. I mean models applied to any kind of data. I want you to distrust statistical modeling.

For if you know a lot about shooting, you’ll easily see the flaws and loose generalizations in these models. But you might not see these flaws when you see “news” reports like “Research shows eating non-manufactured food is bad for you”. You figure the Experts who produce these things must have got it right, because it’s their job. Never be that hasty.

Like I said, here’s my favorite definition of “stopping power”: “% actually incapacitated by one shot (torso or head hit)”. If you take one shot and hit your opponent in the torso or head and he leaves off, well, I count that as a win.

The dark grey are the observed rates. Because the sample sizes varied so much between calibers, some calibers seeing a lot fewer shots, I used a very simple predictive model (based on Laplace’s law of succession) to smooth out the variation. That’s the light grey. Not that different.

The red insets are fatality percentages. The 22 LR are all handguns; and the Rifle are any centerfire. It was all kinds of shotguns, but 90% were 12 gauge.

This is our statistical model. The model includes the data that goes into it, and all the circumstances of that data, and a lot of other implicit premises we’ll come to. (Yes! The data is the model, too.)

So, if your definition of “stopping power” is incapacitation after one shot, then, according to this model, you should use a shotgun and never use a 9 mm.

Yet in Reality, the 9 mm is the most popular cartridge. And you never see—not yet, anyway—people strolling down the street wearing an Ash boomstick back holster. (I want one of these.)

There’s an implicit premise right there: circumstance. You are not, or not usually, out and about with a shotgun (more’s the pity; and I unknowingly originally wrote shotfun), but many wander around with 9 mms. Ellifritz also mentions another circumstance: a lot of that 9 mm data is “ball” or full metal jacket ammo, which is no longer carried that much, giving out in favor of some kind of hollow point (or the like). And anyway, a 9 mm round of any kind is never going to beat a shell loaded with buckshot or a slug, given equal shot skill and placement.

Now this is not the only definition of “stopping power”, and because it includes a hit to head or torso, it is too specific. Because many people miss. Even I myself have had targets change location after I pressed the trigger.

So a second definition is number of shots until incapacitation, where a shot is not always a hit.

Same color scheme, where here it is the average number of rounds until incapacitation. (I’ve ignored the formal model here, since we only have reported means.)

What’s this? A .22 LR better than a 9 mm? Again, this is conditional on the model, with all its implicit premises. One is accuracy: .22s were 62% accurate at hitting the head or torso, and 9 mm 74%. Which doesn’t make any sense. Unless it’s because—and here are more circumstances—that 9 mm FMJ ammo is just passing right through and causing less pain than the .22s, which (according to the many tests I’ve seen) would tend to stay insides bodies. Ouch. So you need shoot less. Could be.

Anyway, the shotfun comes out on top (on the bottom) again.

Perhaps the shotgun has better no-shot stopping power, too, particularly the pump-action shotgun. You can always shout “I have a gun” with any hand gun. But that sound, that very peculiar satisfying sound, a shotgun makes as you cycle a round into the chamber. Well. That can be mighty discouraging to an opponent.

All models only become valuable when they are used to make decisions, and those decisions turn out to be good ones.

I have a Mossberg 590S Shockwave by the bedside, with 2 buckshot minis, followed by 4 slug minis, and topped off by 2 more buckshot minis. I like the symmetry.

By the bedside? Yes. Late, very late at night, it sings to me.

What’s your decision?

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  1. john b()

    New York is seeing to it that ‘stopping power’ fails in all dimensions

  2. Manetti

    Bedside – 357 Mag x 6
    Nearby- 12 ga OO Buckshot x 8 RDS
    Also- 45 HP. 8 RDS Back-up CQB

    On the two occasions requiring active display of weapon, neither required firing a shot.

    The miscreant I found in my bedroom closet recognized the .45 1911 Colt for what it was and surrendered immediately!

    The other event involved a bicycle borne person approaching with malevolent intent around midnight; he fell off the bicycle in his haste to stop upon seeing the 1911.

    Both the above were arrested almost immediately.

    As mentioned, the mere display of a weapon has a serious preventive effect on would-be criminals.

    I believe deadly force should be employed only in the gravest extreme… that is, my life or that of an innocent is threatened, to include imminent bodily harm. Then center of mass until the threat is eliminated.

  3. ensitue

    Chicago ‘wins’ again!

  4. bob sykes

    My favorite gun study. Ellifritz also talks about deterrence, which means your opponent goes away after being shot or seeing your gun. If deterrence is the goal, all handgun calibers are equally effective.

    By the way a 22LR fired from a pistol will go through several layers of drywall, so while it’s not a 44 mag, it’s not negligible either.

  5. Zundfolge

    Looking at the “Average number of rounds to incapacitation” chart, the difference between 9mm and Shotgun doesn’t seem all that great. At least not great enough to worry about (unless the shotgun stats are skewed upward by silly things like .410 revolvers :p ).

    In most (if not all) self defense shootings, the “First Rule of a Gunfight” still applies (that rule being “bring a gun”).

    Bedside: AR15 (WWSD carbine w/30rd of 5.56mm. A SIG Romeo 5 and Surefire G2 attached).
    Also bedside (in a holster attached to my belt in my pants on the floor*) is whatever the EDC du jour is. Currently that’s a Steyr M40 (12+1 .40S&W), but quite often its a SIG P365 (10+1 9×19), and if I’m feeling saucy its a 4″ Chiappa Rhino in .357mag x6).

    As for the idea that a pump shotgun has great “no shot stopping power” … I’m a firm believer that defensive guns should be stored with loaded chambers. When you need one you need one RIGHT EFFING NOW and often will be awakened from a deep sleep so your fine motor skills will be lacking. Point and shoot works better than trying to fumble with a pump release and then pump. Also, while some people will be frightened by the pump action sound, serious bangers are just pissed off by it and you’ve also just given away your position and status as armed so you may get a “shoot first” response.

    *“Always leave your clothes and your weapons where you can find them in the dark.”
    -Lazarus Long

  6. Briggs


    Everybody, and I mean every body, respects The Judge!

  7. McChuck

    As for The Judge, see Paul Harrell’s collection of Youtube videos testing that particular weapon. Spoiler – it doesn’t perform well at any task beyond about 5 yards.

    What do I keep at my bedside? Not saying, except that I have options. And a good flashlight.

    Home defense tip – You are not clearing house to house in Fallujah. You are defending your home. When in doubt, turn on the lights and announce in a loud clear voice, “I am armed. Who are you and what are you doing in my house?” Your lawyer will thank you later. And you’ll be less likely to shoot your own teenager, up to some mischief in the middle of the night.

  8. Gunther Heinz

    In my study wearing a mask stops bullets covered with droplets but not bullets floating in the air.

  9. Cloudbuster

    Another factor this study doesn’t account for are differences in the shooters. People are not interchangeable widgets. How many of the 9mm shootings are A) military, where throwing a lot of lead downrange is more likely, B) Gang-related where spray-and-pray drive-bys are common?

    Are the kinds of people who fire a .22 LR pistol in a fight, and the kinds of fights in which they become involved, materially different from the 9mm users?

  10. Zundfolge


    Usually in these kinds of studies, the figures come from civilian and/or police shootings, not criminal shootings.

  11. Cary D Cotterman

    I find the high performance of .22 LR, when compared to the larger, center-fire rounds, a bit hard to swallow. I just can’t buy into that. If that’s real, then maybe my .22-pellet air rifle is a more lethal weapon than I thought. It sure stops squirrels in their tracks.

  12. Zundfolge

    @Cary D Cotterman .22 really improves performance when you put a 3 after it 😉

  13. spetzer86

    ” from every shooting I could find” EVERY shooting. I wonder if that would include self-inflicted? At that point, a 0.22 to the head from a distance of less than a couple of inches would have a high hit rate, high lethality and certainly wouldn’t need very many shots. Wouldn’t explain the 9mm data though as you’d think those would be at least as common.

    Otherwise, the 22LR data is just strange. I mean, a 22LR pistol isn’t rare, per se, but it wouldn’t be most people’s first choice. They are easy to shoot, but the round isn’t going all that fast due to the short barrel length.

  14. it's all fun and games until the 3am vote comes in

    “shotfun”. indeed!

  15. An assassin (government) I’ve communicated with had two ways of dispatching. A .22 Woodsman with suppressor, and a Sterling SMG in 9mm.
    When unleashed at the torso, the Sterling in 9mm had excellent stopping power.
    More than the same round in a semi-auto pistol.
    Quantity is a quality of its own.
    Keeping that in mind, I’ve come to regard my large capacity semi-auto MP5 clone in .22 as acceptable home defense. Rapid fires at a significant rate with no muzzle climb. At the range Saturday it tore a half dollar sized hole in the center of the target in rapid fire.
    I don’t expect body armor on a burglar.
    The Ar-15 pistol in 7.62×39 with a green laser is for those situations where I expect body armor.
    But I can’t carry those, or a shotgun
    Then it’s my Taurus GC3 which can be had for $230 with 12 rounds + 1 and a laser for $100 all of which fits in a pocket. Any pocket.

  16. I have a fetching pink aluminium baseball bat since, sadly, I don’t live in a civilized jurisdiction. Amusingly it was advertised at the hardware store as a self defence weapon. My 4-Cell D Maglite is probably tactically superior but I can’t resist the prospect of beating a miscreant to death with a pink baseball bat.

  17. Mens Bellator

    Mossberg with buckshot and slugs on the side of the bed for when I bunker in. Glock 9mm on the dresser for if I have to go hunting.

  18. Of course I should favour you with my extensive firearms expertise: the 9x19mm is a sub machine gun round. .380, 9mm Mak, or .38 special if you prefer a revolver (being more suitable for those less interested in guns and more interested in being safe) are far superior in practical use. The lower powered cartridges are more than adequate to the task of incapacitating humans, especially with modern bullet construction, and with lower recoil impulse. The added advantage of .380 / 9mm Mak is straight blowback operation for pistols meaning they’re cheaper and less complicated to make and can be more mechanically robust.

    For military purposes body armour penetration is a consideration nowadays and the 9x19mm generally falls short on that so has no advantage in that respect over lesser calibres. For defence against wild animals such as bear or larger herbivores you might need something more spicy but you should be using a rifle for that.

  19. ensitue

    The trials from the old days speced a 38 SPL w/a 200 grn lead bullet as superior in a 2″ barrel.
    So Big Slow Bullet vs ‘High Velocity’ lighter bullet from a 2″ barrel …
    No one shoots a 38 these days. Regardless, bullets on target, bullet placement in the vitals counts for redress of insults

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