Caleb's Rules of Stopping Power

Caliber wars are fun. I’ve been cruising The Wretched Hive of Scum and Villainy lately, and for whatever reason there are multiple threads in which some guy rolls in with the assertion that “ROROROR .40 SUXXORS”, while at the same time asserting that the 9mm is a superior caliber.  To the .40.

Whenever people start talking about which caliber is “the best”, usually you’ll get three-five solid forum posts about relative muzzle energy, felt recoil impulse, etc…and then after that it just turns into a free-for-all, with everyone chiming in on why “Caliber X sux” or “Caliber Y felled an elephant with a 1-shot stop”.  After the “five post” boundary, you’re also going to find a lot of refernces to “hydrostatic shock”, “temporary wound channels”, and fun stuff like that.

Which leads to Ahab’s Rules for Stopping Power – this is how I select my carry and defensive catridges:

  1. You have to hit the target for the bullet to do any good
  2. The bullet must penetrate deep enough to reach vital organs (aka the stuff that produces rapid stops)
  3. If penetration is equal (i.e. two projectiles that penetrate approx 16 inches) then a larger diameter bullet is superior, as it crushes a greater volume of tissue.

So, to put it in general terms, “penetration is king, but a big fat bullet is nice”.


  1. Velocity can be an important component as well. Probably more than the (expanded) diameter. The original diameter of the bullet (in the 9mm, .40, .45 set) isn’t that big of a factor. Think of it this way, converting all to mm we get 9, 10, and 11.4 mm diameters for those bullets. Another mm of diameter of tissue damage just doesn’t mean that much in terms of the time it takes to stop the attacker (bleed out being the mechanism). If you got a CNS hit then it probably doesn’t matter which sized bullet was used. A skeletal hit is the one case where it probably matters but it’s not really the diameter of the bulle that makes the difference but the momentum of the bullet. And the greater mass, with approximately the same velocity, is more likely to cause larger fractures.

    If you want to talk expanded (HP bullets of course) diameters then the diameter differences (and corresponding areas/volumes of the of tissue damage) then the diameters probably make a noticable difference. But the question of whether it expands and how much become the critical items rather than the original diameter/caliber. A 9mm that expands (and penetrates) in soft tissue is better than a .45 ACP that doesn’t expand.

  2. I absolutely agree about velocity – that’s why I believe that the most important factor is penetration. A bullet has to be moving fast enough to get to those central nervous system parts, or the heart for it to matter. If I shoot someone with a hypothetical .50 caliber that is going so slow it only penetrates one or two inches, that’s almost useless compared to a .25 that penetrates 16 inches and hits the heart.

  3. As a friend of mine says, you can get a 9mm to expand all you want, a .45 won’t get any smaller.

    Let the flames begin.

  4. Numbers and dick-waving aside, multiple 9mm JHPs will cause most people to reconsider their current activities, and I am ok with that.

  5. Any caliber discussion that does not take into account:

    1) Effect of jacket design, material, and hollowpoint cavity shape and size on bullet upset…


    2) Sectional density, momentum, and its effects on penetration…

    …is usually my tipoff that the material is being discussed by folks who haven’t done much studying on terminal ballistics.

    Given the fact that most modern LE-oriented loadings are all engineered to pass the same protocols, caliber discussions attempting to choose among most service calibers these days are really just so much mouth music.

  6. May I suggest the Zeroeth Law of Stopping Power: Have a gun with you and be willing, prepared and able to use it.

    To quote an old friend, who would you rather face: Woody Allen with a .45, or Clint Eastwood with a .22?

  7. Everyone knows that “Real Men” only carry 44Mags or larger, like the 480Ruger or the 500SW. What sort of loser carrys a 32acp or 380.

    Enough kidding now, A slow hit with a small caliber is massivly better then a Fast Miss with a Large one. Carry as much gun as you can shoot good enough. For years i carried a 1911A1(45acp), then i lost some weight and carried a 38spl(rossy snubby). I never felt under armed.

    Bottom line, carry what you want, and hit your target. Its all good.

  8. Back when the large bores became popular (thanks to Dirty Harry) a question came up in one of the NRA classes as to which was the better short-range weapon – the .357 or .44 Magnum?
    The reply was, “A 12 ga. sawed-off shotgun with 00 buck. That would kill anything in a 15 foot circle at 25 yds. and would not have the worry of muzzle flash or kicking off target like the pistol would.”
    I tend to agree.

  9. The best argument I ever heard about stopping power was that being hit in belly with a 22LR was more of a deterrent to continued action than being missed by a 45ACP. The first rule is the most important rule – only hits count.

  10. ““A 12 ga. sawed-off shotgun with 00 buck. That would kill anything in a 15 foot circle at 25 yds. and would not have the worry of muzzle flash or kicking off target like the pistol would.””

    Was the instructor being sarcastic? I hope so, because buckshot only opens up at about an inch every yard or so, depending on the load and choke (they tend to open up a little faster with a cylinder bore choke and unbuffered, unplated pellets, and a little slower with an improved cylinder or modified choke and buffered, plated pellets).

    In other words, you still need to aim, and it ain’t going to kill anything if you miss.

    That also brings up one simple fact: all handguns suck for gunfights. We carry them because they are far more convenient than a three foot long twelve gauge or a carbine, and therefor comply with the “have a damn gun to begin with” rule.

    However, they are all extremely anemic and difficult to aim compared to long guns. so the most important factor is shot placement and that you have ammunition capable of penetrating deep enough to hit vitals, not caliber.

  11. Tam, I think those variables can be simplified into tests of expansion (or more accurately–creation of a “large enough” wound channel) and penetration. If it expands and penetrations it doesn’t really matter what the materials and construction details are. And, as you indicated, all modern “premium” self-defense ammo is tested using the FBI protocol and either meets the standard or isn’t viable in the marketplace.

    Bullet penetration is roughly proportional to the bullet weight times the velocity to the 0.6 power (see Duncan MacPherson’s book Bullet Penetration). So bullet weight is a little more important that bullet velocity in terms of getting good penetration.

    The bullet velocity matters because that is the primary indicator for creation of a permanent stretch cavity. Of course the velocity threshold varies considerable depending on whether the bullet is traversing something like muscle or some fragile internal organ like the liver.

    See also The Great Bullet Debate which I wrote over ten years ago.

  12. And, as you indicated, all modern “premium” self-defense ammo is tested using the FBI protocol and either meets the standard or isn’t viable in the marketplace.

    True, but a lot of folks don’t realize that there is plenty of ammo out there that is not designed to meet these criteria, predates the FBI protocols, or offers dubious performance (Glasers & MagSafes, Pow’R’Ball, EFMJ, all the older JHP designs still floating around and being loaded by smaller companies like CorBon or in the budget lines from big companies, 2nd Gen bullets like the original HydraShok, bullets loaded outside their performance envelope,such as hot-rodded Gold Dots from boutique companies, et cetera…)

    But, yeah, if someone buys LE Rangers or Partition Golds, Gold Dots or Golden Sabers in a service caliber, they’re getting a bullet that’s going to reliably expand to .60″+ and penetrate 12″, even after defeating some more common barriers.

    And thank you for the link! It’s kind of a bummer to see Towert’s page is gone. Thankfully I’ve been “right click, save as” at FirearmsTactical since I was doing it on a Pentium 133. 🙂

  13. “Bleed out”/exsanguination is a fairly well studied mechanism but unfortunately it is almost perfectly irrelevant to a handgun discussion; handguns mean civilian use. It takes a minimum of about 15 seconds with a large caliber heart hit. How many rounds can you put on target in 15 seconds, counting reloads? You might as well try to introduce an opponent to smoking and wait for cancer to kill them. Further, if you are using a handgun and have 15 seconds to wait, you were almost certainly not justified in firing.
    (For military/rifle situations, where you’re engaged in a continuing battle from cover, exsanguination is usually very relevant.)

    Unfortunately there is no decently understood mechanism for why people tend to stop fighting immediately after a good hit with a handgun, nor for why they sometimes don’t; we’re still guessing in the dark on this. Hydraulic shock was an attempted model, but it didn’t to work out.

  14. Robert – there’s no choke involved in a sawed off shotgun, you’ll get a nice pattern @ 10-15 yards – and will kill just about anything you hit. Certainly, one has to aim, but It’s more forgiving (for the shooter not the shootee)

  15. Oneiron,

    Robert – there’s no choke involved in a sawed off shotgun, you’ll get a nice pattern @ 10-15 yards

    An open-choke 12-gauge at ten yards will put all nine pellets between two shirt buttons. That’s not noticeably any more forgiving than the much-easier-to-shoot carbine, as most LE agencies have discovered.

  16. Numbers and dick-waving aside, multiple 9mm JHPs will cause most people to reconsider their current activities, and I am ok with that.

    Conversely, multiple 9mm FMJs don’t do jack. I’ve met a former student of the man that taught me to be an instructor who was shot 8 times in the torso with 9mm FMJ. If it had been hollow point ammo, he’d have been dead shortly after that. Instead, he was actually able to fight off his attacker and live.

  17. Oneiron – last time I went to the range, I tested expansion patterns using Federal Vital Shock and Remington Express 00 buck. At 25 yards, my patterns with the Federal loads were around 8-10″ at their widest, using an improved cylinder choke. At 15 yards, they were doing 4-6″.

    The longest shot possible in my apartment is around 13 yards, which means the pattern is unlikely going to open up much past 3-4″.

    The Remington Express groupings were quite a bit wider, at 14″+ at 25 yards and 8-10″ at 15 or so yards. However, I consider this to be a bug, not a feature.

    Being that I live in an apartment, I have to account for every single pellet that leaves my shotgun. Because of this (not to mention the benefits to terminal performance), I want every single one of them hitting the BG, not flying off into the ether landing who knows where. This means I have to aim, and not trust to some illusionary cone of death.

  18. When it comes to this subject, I usually have a different opinion than everyone else and it all comes down to “What Have YOU Killed With A Handgun, ANY Handgun???”

    And I don’t mean ‘oneies’ and ‘twoies’ either. JD Jones has killed thousands upon thousands of animals, most of ’em BIG. That’s why all his cartridges are BIG and POWERFUL as well and often shot only in single shot pistols….they are the only thing that will contain them at ignition. Yet, it is his experience that I respect. His stuff works because of this experience.

    How does this translate into common self-defense rounds? Simple, carry the gun you want and shoot stuff with it. A lot of stuff. If you can’t hit a small animal with your favorite blaster, what makes you think you will be able to make a head shot when it really counts? If you have moral qualms about indiscriminately shooting small non-threatening animals what makes you think you will be able to drop the hammer without thinking? Out of pure reflex?

    Remember, self-defense is just like playing sports if you have to think about the specific move, you’re already too late and way behind the power curve!

    As for shotguns and their fabled reliablilty at ending fights, I’ve already mentioned on my blog how 19 pellets of #4 Buck out of 27 in the shell completely missed a lethan force subject in less than the length of a Crown Vic patrol car.

    The biggest failure with the shotgun is the ammunition, not the action or the choke. Most often the wrong ammo is in the gun and when the right ammo is IN the gun, it’s out of date or out of condition due to the out-of-round pellets in the load from having bounced around inside a vehicle for a number of years. There is a reason few military forces use a shotgun in lethal force situations.

    When someone can document having killed 50 dogs over a period of months with their favorite load and hand blaster, and what the response or outcome was. I will listen. Not because they got to play with 10% gelatin on a warm Sunday afternoon or listened to rocket scientist spout off on the worldwideweb.

    All The Best,
    Frank W. James

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