The Lowdown on ‘Knockdown’ Power (It’s Not A Real Thing)

Editor’s Note: The following is a syndicated article by author Ed Combs that first appeared in USCCA’s Concealed Carry Magazine Volume 11, Issue 8, November/December 2014 under the title, “Lowdown on Knockdown.” 

The single most common question I get from new shooters who wish to acquire a sidearm for self-defense is a very general “what should I get?” I tell them that in my opinion, the short answer is “the largest autoloading pistol you can comfortably carry, conceal, and shoot” and that the long answer is “that depends.” The next question is always about “knockdown,” and I tell them there is no short answer for that one.

The other side of that coin is the Knockdown Devotee. I cannot begin to count the number of times someone’s told me—often without my even asking—that they carry a .45 (or a .357 Magnum or a 10mm or a .44) because “even if I just hit him in the arm, it’ll spin him around and knock him down.” We recently got a Facebook comment asserting that the .38 Special will “flat out knock a man down”—not from personal experience, of course, but we were assured they had it on good authority from a “big Deputy Sheriff from Oklahoma.”

The problem is that though such claims are not categorically inaccurate, such claims are also not dissimilar to the intro of the old Superman television show during which the Man Of Steel grabs the barrel of a villain’s revolver and bends it as if it were made of licorice. (This is because the barrel of said revolver was, in all likelihood, made of licorice.) Though it wowed millions of children in the 1950s, there’s a Newtonian physics issue in play: when it comes to physical force, actions result in equal and opposite reactions. What this means is that for Superman to bend the barrel of that revolver as depicted, the hand holding the other end would have to be as strong or stronger. If not, the much stronger hand would simply twist the gun out of the much weaker hand, ruining the intro and revealing that Superman was really just some Standardman in pajamas and a cape.

Before we go any further, though, I’d like to address the elephant in the room.

I am neither a combat medic nor a trauma surgeon. As such, I am not qualified to comment on the topic of Hydrostatic Shock—the theory that a projectile entering the body at a certain speed transferring a certain amount of energy creates a shockwave of sorts that causes remote damage to areas outside of the immediate wound channel. The only comments that I can offer are that it sounds like something that could be true and also sounds like something that could be false. I know and respect several individuals who have been in the actual man-killing business who feel the same way. Until evidence agreeable to all parties can be isolated, that’s all I’m going to say. What I am addressing here is a phrase that I unfortunately hear time and again: “Even if I just hit him in the arm, it’ll spin him around and knock him down.”

In order to hit an attacker with a projectile that would literally spin them around and knock them down, the average concealed carrier would have to up their game a bit. Tough part is, most even slightly portable firearms that are capable of doing so went out with the 19th Century.


Before the advent of modern smokeless powder and jacketed bullets, men regularly went out after elephant, rhino, and other such thick-skinned dangerous African game with rifles measured in bore rather than caliber. In this context, “bore” referred to the number of lead balls the diameter of the gun’s bore required to make a pound, so a 4-bore rifle fired a 4-ounce ball, a 2-bore rifle fired an 8-ounce ball, etc. This had to be done because before smokeless, the only way to deliver more energy to a target was to just make everything bigger—the projectile, the powder load, and the firearm itself. Complicating matters, the only bullets available at the time were round or conical bare lead slugs, and the pinnacle of available technology was lead alloyed with antimony. Even thus modified, it was still difficult to make bullets that would not deform under the enormous pressures generated by even higher powder charges, so big and slow was the order of the day.

The result was comically enormous firearms that looked like beefed-up double-barreled shotguns (because that’s exactly what they were, though with rifled barrels). Cartridges the size of small thermoses were common. Regularly weighing over 14 pounds, the physical experience of firing one even by an experienced professional hunter ranged anywhere from “punishing” to “I now have a nosebleed, a concussion headache, and am facing the opposite direction from when I started.”

These rifles fired enormous projectiles at relatively low speeds that were capable of stopping a charging Cape buffalo with a well-placed shot. As such, I am comfortable stating that were you to fire one at a human attacker and only hit him in the arm, you might well spin him around and knock him to the ground.

All of this is pointing toward one reality: unless someone tells you that they crossdraw carry a 4-bore in a saddle scabbard under an enormous overcoat, their claim of being able to spin an attacker and drive him to the ground with a single shot from their daily CCW firearm is extremely dubious.

So, handgun rounds as manstoppers: can a threat be more effectively stopped by one round of .357 Magnum or .45 ACP than it can by one round of .38 Special or 9mm? You could probably say that history supports that argument (and that the associate editor of a gun magazine you read agrees). One-shot knockdowns? I’m here to tell you that they were and are relatively uncommon, and when they did and do happen, it usually isn’t because bullet met brain stem.


Now, this is not to say that no one has ever taken a bullet to an extremity and immediately toppled over. Quite the contrary in fact, and in order to understand why this happens, all you need to do is watch kids run or attend a high school hockey game.

Say two 6-year-olds are playing tag. One is running as hard as she can and as she is doing so, her friend tags her elbow, sending her sprawling like she hit a tripwire. This is one of the many areas in which small children at least appear to defy the physical laws of the universe: she was barely touched, so why was the result so catastrophic?

That running child did not fall because of the amount of force that was applied to her elbow. A particularly aggressive raindrop or blade of grass probably could have delivered the same result. She was concentrating on one thing—“I need to be running as fast as I can right now”—and as a result didn’t have any attention to spare on maintaining the inner gyroscope that keeps a more relaxed and attentive person upright. This is how the 6-year-old falls when her elbow is tagged, but an NFL running back can drive his way through three or four men who are paid handsomely for their acumen in the field of grabbing and smashing other men to the ground.

She wasn’t knocked down…she lost her balance.

Along those lines, I played competitive ice hockey for many years. Though the most crushing hits in a tournament were usually courtesy of some Sasquatch from the Iron Range of Minnesota or a Skookum that strayed down out of the BC rainforest, every now and then someone would whip through a corner past another player and, without warning, appear to be shot sideways out of a cannon. Several parents would scream for a penalty that wasn’t going to get called, and officials would sometimes even have to skate over to the glass and explain to irate moms and dads that there hadn’t been a dirty hit or even a questionable one. What had happened was simple and fairly common: the player that was only now regaining his feet was skating as fast as he could force his athletic 17-year-old body to go, touched the toe of one skate blade to the puck as it slid under his feet, and basically managed to fall down an entire flight of stairs in a third of a second.

He wasn’t knocked down…he lost his balance.

So why do we continue to hear these claims of murderous attackers dropped like 2-foot putts by cops and private citizens who appear to possess sidearms from Thor’s hammer factory?

Like so many discussions on this topic, it comes down to shot placement and what exactly an attacker was doing when a bullet impacted their body. Ask any coroner or Chief of Police: some people get shot with a .22 and fall over never to rise again, and some people absorb as many as a dozen or more .45 ACP jacketed hollow-points and survive to fight another day (or spend a good long hitch in prison). Though the .22 LR is undoubtedly an inferior self-defense round when compared to the .45 ACP, neither of them play as large a role as the mindset of the individual receiving the bullets, placement of those bullets in that individual, or—in the case of that individual keeping their feet—whether the introduction of those bullets into their body resulted in a loss of balance.

Now for the actual one-shot stops.


When an attacker is actually dropped with a single shot and they neither grunt nor stir—when they receive an immediate or near-immediate mortal wound from one shot delivered by a handgun—it is almost invariably a shot delivered to the index-card sized area of the front or back of the head that allows access to the brain stem. When this is destroyed, or when enough catastrophic damage is delivered to the brain itself, the central nervous system is no longer capable of sending any messages to any part of the body and the show’s over. This is basic, this is fundamental, and there isn’t really any way of an attacker “toughing it out” or “just deciding he’s not going to die today.” Such feats of human endurance are possible when other tissues are damaged—even the heart or major arteries resulting in monstrous blood loss—but as soon as the brain is taken out of the equation, the body will cease functioning extremely quickly. As it’s often described, it’s like someone cut the string.

Though this is extremely difficult to prove, an acquaintance of mine who has served as a County Sheriff, a U.S. Marshal, a Colonel in the U.S. Army, and as an overseas security contractor in war zones has another very interesting theory. He hypothesizes that many of the one-shot stops he’s seen or heard about were less likely caused by the impact of the bullets or pellets, but rather by acute stress-induced heart attacks experienced by already medically compromised individuals. In his lines of work, recipients of fire were rarely calm and surprised by their contact, but rather extremely agitated and fearfully anticipating the impact of incoming rounds. I don’t know how I feel about this, but I do know that this magazine is read by more than a few medical doctors—let me know what you think.

No one who is versed in armed self-defense will argue against the .45 ACP or the .357 Magnum as supremely capable defensive cartridges. I have total confidence in the .45 automatic that lives in my nightstand and an S&W Model 19 .357 Magnum has been my woods gun for more than a decade. I love both cartridges, and I will enthusiastically state their case before any court in the land.

I merely ask people to cease claiming they’re loaded with magic beans.

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{ 18 comments… add one }
  • Dave January 21, 2020, 1:00 pm

    I enjoyed the article. Thanks. And as pointed out, the laws of physics- 2nd law of thermodynamics I believe -states for every action there is an equal and opposite reaction. So when sillywood shows someone being blown backwards by a shotgun blast by all rights the shooter holding the gun would also be pushed backwards by the gun. You can argue the merits/effects of the different calibers all day, but truth is the well placed shot is the critical issue. The author mentions the finality of the head shot, and rightly so. But lets face it; the average person in a self defense fight with adrenaline flowing a the deer in the headlight frozen stance just is not likely to achieve such a shot. Center mass double tap, or more pulls on the trigger, is going to be the most effective one can hope for regardless of the caliber. Practice, practice, practice at the range, at home with your draw, moving to get out of the way, this is the path to surviving a gun fight regardless of caliber.

  • Michael Gothard January 18, 2020, 12:16 pm

    Choose a weapon that you are comfortable with shooting and carrying. It doesn’t matter if you have a .22 or a .44 mag if it’s at home when you need it. My choice is a 9 mm with 11 rounds, Should cover all bases.

  • BRASS January 18, 2020, 12:08 pm

    If talking about field artillery, I would agree.
    With any firearm or weapon that anyone is likely to actually use, the answer is NO – Knock down power is a misnomer, at best.

  • John lacey January 18, 2020, 8:37 am

    Not sure about knockdown power! But I am certain that it takes more than one 22 rimfire to stop a dillo ruining My yard or field! One 9×25 dillion out of a glock 29sf stops and totally renders a dillo out of the fight! What it does to a human I have no clue and hope I never have to find out!

  • Mark Wynn January 17, 2020, 11:23 pm

    Your discussion on pistol bullets “spinning around” someone I found reasonable and useful.
    However, as far as the terrible damage inflicted by high-speed rifle bullets creating “hydrostatic shock”… that’s not conjecture. It’s been well-verified by the reports of many emergency room and military physicians, and the horrible wounds they encounter.

  • Zeno Streletz January 17, 2020, 5:22 pm

    Years ago the “American Rifleman” tested all sorts of calibers using a dummy on wheels.
    The up-shoot was that it took a very big rifle to even move the dummy. All this was done
    a very long time ago.


  • sigmundsauer January 17, 2020, 4:57 pm

    I believe many, if not most, one-shot-stops are a result of people choosing to stop – because getting shot hurts and is not good for your health. Some rounds are more effective at communicating to you that “this hurts!” and “I’ve been shot!” are more likely to psychologically influence you through pain or force that I should not continue on the present course. This can obviously happen regardless of caliber, .22 LR or .357 Mag, but some are inherently better than others in persuading people to stop regardless of mechanisms of injury. Shoot, there’s an argument to be made that the legendary .357 Mag amassed such a mythical reputation perhaps just as much attributed to its fearsome muzzle blast vs. any transferred energy. A snubby .357 Mag is scary!

  • Bad Penguin January 17, 2020, 3:57 pm

    My friend you are fighting a losing battle with Hollywood. Articles like this have been around for decades and they still persist because of movies.

    Big Game hunters have related how they shot leopards standing on a tree limb and cat dropping in place on the limb. There is no such thing as knockdown power just legality.

  • ERDOC January 17, 2020, 2:39 pm

    Bullets kill in only two ways, they crush tissue in it’s path, making a permanent hole, and by stretching tissue. Most tissues have elastic collagen, and rebound, but if stretched beyond their limits, it will tear. Some tissues lack elastic properties ( brain, bone, liver, spleen, pancreas) so when stretched, do not rebound and leave a bigger hole. The endpoint of crush and stretch is blood loss; the bigger the hole the faster you bleed out. This is why you shoot center of mass(mid chest). Massive blood loss targets are mostly here – heart aorta, vena cava, top of liver,top of the spleen, and pancreas. Head shots are even better, ( but a smaller target), because if you disrupt the bodies electrical system, the body shuts down immediately. But knockdown power means nothing, A persons ability to withstand trauma varies with the individuals psychologic makeup as well well as their physiologic state (drugs, anger, rage, fear, adrenalin surge, etc). I’ve seen a person with his intestines hanging out to the floor fighting with six police and security guards because he wanted to leave and get even with someone. On the other hand, I’ve seen a normal healthy person in shock because they stubbed their toe and tore their toenail off – sweating, screaming, hypotensive, and vomiting.
    Bullets: as you stated in your article, don’t have enough mass to knock a person down. They have the velocity but need a lot more mass. This is a simple transfer of momentum. Consider a 30-06 150 grain bullet. It hits an individual weighing 150 pounds, thats a 1,050,000 grains object (7000 grains per pound). Not going to have much of a energy transfer. Now consider a car only traveling 40 mph weighing 2000 pounds or 14 million grains. Thats almost 14 times the mass of the person. In this case the person will be airborne. Forty mph is considered lethal for most car/pedestrian accidents.
    As far as shockwaves destroying tissue, histologic examination of gunshot tissues shows that cellular damage does not typically exceed more than 0.5 cm beyond the wound track, regardless of the caliber of the weapon used.
    For evidence of lack of knockdown effects, there are multiple gruesome examples on web sights which show German soldiers executing prisoners in WWII, as well as other sights showing people executed by firing squad; no one gets spun around or blown backwards, they just drop.
    Summary; forget knockdown power, disconnect the body’s electrical system with a shot thru the brainstem, or make a big hole in an area with lots of blood supply.

    {ER Doc in level one trauma center for 40 years}

  • michael hayes January 17, 2020, 1:52 pm

    An anecdotal story, a buddy of mine, in Vietnam, was just outside jungle cover, in a field, starting taking rounds fired at him, started running and felt a sting in his lower leg, he said he increased his speed by half, ran for another 50 yards, got under cover and then collapsed, turns out he had been shot in the lower leg with some of it missing, but he thinks adrenaline kicked in, it didn’t turn him around, didn’t alter his path, but he did receive a medical discharge with part of his muscle missing. So yeah, really depends on circumstances.

  • Wayne January 17, 2020, 11:49 am

    Good article. You missed a couple of other myths commonly seen in movies which would be good fodder for another article: being blown back several feet when hit with a .44Mag or similar large caliber bullet and those sparks created when a bullet hits or deflects off another solid object.

    • Mark Wynn January 17, 2020, 11:27 pm

      but but … how will we know where the “bullets” are striking if special effects doesn’t provide sparks, holes, dust or spurting blood?

  • Tommy Barros January 17, 2020, 10:41 am

    But you can take that .357 Mag round and SHOVE IT!
    OH YES I have heard all the ANTIDOTAL STORIES about so called actual shooting experiences, BUT they are NOT GOOD EVIDENCE!

    • Michael Keim January 17, 2020, 12:40 pm

      Your hate for the 357 mag has blinded you to the facts. The 357 was developed in the 1930s because the police wanted a more powerful cartridge. J. Edgar Hoover was given the first 357 mag made by S&W. Through the 60s and 70s most law enforcement officers carried the 357 mag. The 125 grain load has held the record for best fight stopping round.
      If you don’t like the 357 mag that’s you’re choice however do some research before you start ranting.

    • Don January 17, 2020, 3:28 pm

      You don’t know much about the .357 Magnum. Penetration is determined by bullet properties. A 110 gr. JHP usually wont penetrate well at all. I had to shoot a small dog. The bullet hit the jaw and made a horrible, non-killing wound. Penetration was terrible. I shot the dog again in the body to put it out of its misery. Over the years I’ve had to shoot injured dogs and deer. The worst performer was the .44 Special with factory ammunition. The best performer has been .357. It just takes a good JHP bullet of 125-158 grain. It is a horrible thing to have to do. But I’ve been placed in that position more times than I like.

    • Andrew N. January 21, 2020, 1:31 am

      I read a study awhile back about which caliber was “The Best” for killing a human. There wasn’t one. Everything from a 22LR to 45ACP plus the “everyday” magnums was included. (It even included the .25ACP, as hard to believe as that is.) Shot placement was the ONLY factor that mattered. Period. Although it’s not an EDC weapon, I love my Marlin 1895 45-70. I always figured if it works on American Bison…My EDC choice is a .40 S&W in a Firestar. A little heavy, ( but so am I) but the weight-mitigated recoil helps with follow-up shots, and I just prefer steel over plastic. ( It’s a preference, not a challenge to you polymer fans out there. To each their own, I always say.)

  • Daniel G Braatz January 17, 2020, 4:48 am

    Excellent! Well-written, informative & entertaining!

  • Will Drider January 15, 2020, 5:15 pm

    Though this Article was first published before the FBI’s most recent selection (back to) a 9mm handgun BASED COMPLETELY on Magic Beans, it still rings TRUE. The performance of Magic Beans must only be considered: as a “Bonus”. Projectiles do fail to perform as designed more frequently than you may think because they can and do encounter an unlimited amount of variables. Before and at the target/threat.

    Chose your cartridge based on performance of Ball FMJ projectile then marry it to a handgun that you can use proficiently and size matching you requirements. After that you can add Magic Beans expecting whatever enhancements they promise BUT the weapon system will never preform less than an acceptable minimum when the Magic fails.

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