What about Kinetic Energy Transfer? Does It Cause Psychological Stops?

Ah, the old “energy transfer” question.  You knew I had to address it sooner or later, didn’t you?  Turns out it was later.  But, I just ran across an interesting article that I think may prove quite illuminating on the subject.

What subject?  Psychological Stops.  As in, why does someone who’s shot superficially, or non-mortally, choose to drop their gun and stop attacking?

It’s an important subject because, while we typically deal with the concept of “incapacitating wounds”, the fact remains that a large percentage of gunfights seem to be ended due strictly to psychological factors, rather than physiological factors (i.e., the person voluntarily decides to stop attacking, instead of being forced to stop attacking.)

How many cases are of psychological stops rather than physical incapacitation?  I don’t know of any definitive study that has attempted to classify it.  I do know that there are doctors who say that (with treatment) six out of seven people shot by handguns will survive.  In a case of true incapacitation (where the person’s body has been so damaged by the bullet that their body itself shuts down and therefore removes their capacity to continue acting voluntarily) the odds would seem to be drastically lower, since true incapacitation usually relies on either the death of, or paralysis of, or the rendering unconscious of the attacker.  And rendering them unconscious usually happens through blood loss so substantial that their blood pressure drops below that necessary to keep them conscious and acting.  And if they’re losing blood that fast (through a damaged artery or circulatory system organ) then it doesn’t seem likely that emergency responders would be able to get there in time to prevent a total bleed-out.

As such, it seems that a very high percentage of people who are dissuaded from their actions via gunfire, do so not because their body has been so damaged that they cannot continue, but rather they choose voluntarily to stop.  (I offer as food for thought my prior articles on just how much damage a human body can sustain and still keep attacking; Peter Soulis put twenty-two rounds of .40 S&W in Tim Palmer and Palmer didn’t stop until the twenty-second round hit him.  It can at times be quite difficult to force a determined attacker to stop just through the use of gunfire.)

Incapacitation vs. Psychological Stops

Before continuing, I want to point out one of my prior articles, “An Alternative Look at ‘Alternate Look at Handgun Stopping Power‘.”  In that article, I attempted to evaluate the data collected by Greg Ellifritz and put some context into it, as far as how the data could not necessarily be used to draw the type of conclusions that people are wont to draw about data like this (such as “the .40 S&W is the best manstopper, and the .32 ACP has a higher one-shot stop percentage than the 9mm”, or any other such conclusions.)  The crux of my argument there was that there was no real delineation in the data between what was a Psychological Stop (i.e., the person shot just gave up) vs. true Incapacitation (which, by my definition, means that the bullet damages the body to the point that the person is no longer capable of voluntary action).  And if we don’t know that distinction, we can’t attribute the performance to the bullet alone.

I believe that in my prior article I laid out some good reasoning for how we couldn’t tell which were Psychological Stops, and which were true Incapacitation.  Accordingly, I think the percentages listed simply cannot be relied upon as a predictor of how effective any particular caliber will be in causing an attacker to stop.

However, I’d like to revisit this subject because of a follow-up article by Mr. Ellifritz (who, generally, I do agree with on almost everything else in his articles).  Ellifritz published an article on the use of his data to evaluate the .22LR as to its effectiveness for self defense, especially in context with answering some questions raised by readers of his prior articles.

I think Ellifritz’s data sheds some excellent light on a subject that’s been the source of many questions for many people, and that is:

Does Kinetic Energy Transfer Cause Psychological Stops?

So here’s the crux of the matter, in a nutshell: there are two different schools of thought on handgun bullet performance, the Light & Fast vs. the Slow & Heavy.  The Light & Fast group typically use terms such as “energy transfer” or “hydrostatic shock” to talk about how a bullet affects a person’s physiology; the Slow & Heavy group generally ignores all that and focuses on what actual tissue was destroyed by the bullet itself.  The Slow & Heavy school (of which I am a member) say that if you poke a hole in someone’s vital organs, they’re going down.  And if you don’t poke a hole in their vital organs, they won’t have any physical reason for stopping.  They MAY choose to stop, but there isn’t necessarily any anatomical reason for them to have to stop.

The Light & Fast group, on the other hand, focuses on the size of the temporary cavity created, and some argue that the faster the bullet “transfers its energy to the target”, the more likely the person is to stop their attack.  The idea behind this philosophy generally involves the notion that a “rapid energy transfer” will cause incapacitation.

I don’t know about that; I know of zero studies that have been done that show that there is any increased likelihood of a psychological stop due to energy transfer, and don’t know how an ethical researcher could even begin to undertake to test for such an effect.  Seriously, such testing could only be conducted against human subjects (since only humans have human psychology), and would likely require a very large sample size before you could filter out the noise and start to see real patterns emerging.  Probably at least a thousand data points would be needed, and I think it’s safe to say we aren’t going to see any researchers shooting a thousand people to see what percentage are likely to just “give up” in a gunfight…

So the question arises — is a “Light & Fast” bullet more likely to cause a psychological stop, than a “Slow & Heavy” bullet is?  Does more energy transferred make a person more likely to quit a gunfight?  Would a fast-energy-transfer gunshot be more painful than a Slow & Heavy gunshot?

Again, these are all questions we cannot answer scientifically, without some serious ethical breaches of protocol!  But, using Ellifritz’s .22LR article, I think we can take a good step towards clearing up some of the confusion and sorting through the fog.

Here’s the thing that stood out to me, in Ellifritz’s studies — while we don’t know what percentage of his data subjects were true psychological stops vs. true incapacitation, we do still have a lot of data to examine on people who were shot.  And, in Ellifritz’s article on .22LR, he makes some insightful observations, specifically that the .22LR is the least likely of all calibers to cause a true physically incapacitating shot.  Due to the small diameter, light weight and low velocity of the .22LR, its penetration capabilities are less than the other calibers are, so the likelihood of it having caused substantial body damage sufficient to cause true incapacitation is reasonably presumably lower than other calibers.

And yet — a whole lot of people in his study stopped attacking after getting shot with a .22LR.  According to his data, 60% of the people who were hit with a .22LR round, stopped their actions.  Only 31% didn’t, regardless of how many rounds they were hit by.

What does that tell us?

Well, it tells me that people don’t like to get shot, and getting shot is frequently enough to get a person to give up.  Even if the bullet doesn’t mortally wound you, the sheer shock and horror and fear of being hit by a bullet (any bullet) and the attendant pain, blood, and fear of imminent death that all can be expected to occur in gunshot recipients, is very likely enough to get that person to say “screw this, I’ve just been shot, I’m not sticking around to get shot again.”

Going by Ellifritz’s data, the percentage of people who stopped after getting shot by a single shot of a .22LR, is about the same as the percentage of people who stopped after getting shot by a single round of .380, or .357 Magnum, and it’s even higher than the percentage of people who stopped after getting shot with a single round of .38 Special, 9mm, .40 S&W or .45 ACP.  Seriously, that’s what the data shows.

How many of those stops were psychological?  We cannot know, the data was not gathered in a way that would tell us that, but seeing as the percentages are relatively quite consistent (from 47% for the 9mm up to 62% for the .22), and knowing that the .22LR is the least powerful of all the cartridges tested and therefore (as Ellifritz eloquently reasoned) the least likely to be doing true physical incapacitation to the attacker’s body, I think it’s fairly safe to say that a whole lot of these 47% to 62% of “one shot stops” were strictly psychological.  Again, this is supported when we look at other shooting scenarios (see my prior articles referenced in this article) where five hits of 9mm or .38 Special, or 7 hits of .45, or even 22 hits of .40 S&W, were not enough to bring an attacker or an officer to the point of incapacitation, it seems unlikely that a single .22LR bullet is likely to drop an attacker through sheer force of incapacitation (without a direct hit on the central nervous system or circulatory organ, that is).

So now we return to the central question of this article — how much of a role is Energy Transfer likely to play in psychological stopping?  Again, and sorry to repeat it so many times but it’s important to be clear on this: we don’t know, and we cannot truly know definitively.  We can only look at the information in front of us and try to draw what conclusions we can.  And the conclusion I draw is: “Energy Transfer” doesn’t necessarily mean squat as far as causing an increased likelihood of a psychological stop.

The reason I say this is specifically because of Ellifritz’s .22 data.  If you think about it, if higher levels of energy transference were going to cause people to be more likely to quit attacking, then shouldn’t the percentage of one-shot stops be much higher for the high-energy rounds (like .40 S&W or .357) than they would be for the tiny-energy .22 round?  Or, let’s put it another way — the .22 doesn’t really have much energy to transfer at all.  From a handgun, the .22lr is usually going to deliver less than about 90 ft/lbs of energy, as opposed to the 300 to 500 ft/lbs one is likely to see from a 9mm, .357 Magnum, .40 S&W, or .45 ACP.  So — if the amount of energy transferred was a strong indicator of the likelihood of a person to psychologically stop, then shouldn’t the 1-shot stop percentages be much higher for the higher-energy rounds?  And yet, they’re not.  The highest-energy round on Ellifritz’s list, the .357 Magnum, has a one-shot stop ratio that’s practically identical to the lowest-energy round on his list (the .22LR).  It’s 61% vs. 60%!  How can those be the same, when a .357 delivers 430 ft/lbs or more, and the .22LR delivers less than 90?  The leading theory to me is: because “energy transferred” doesn’t matter as much as people may like to think.

Surely the .357 creates a much bigger temporary cavity.  Surely the .357 delivers more pain and transfers more energy — heck, it’s got about 5x as much energy to transfer.  And yet… according to the numbers, the (fundamentally) same percentage of people hit with the low-energy round stopped attacking after one hit, as those who were hit by the high-energy round.

One could argue that a higher percentage of the .357 bullet recipients were incapacitated overall than the .22LR bullet recipients.  While we cannot know for sure, the data does show that while the one-shot-stop percentages were fundamentally the same, the % of those who “would not stop no matter how many times they were shot” is much higher for .22LR than it was for .357 magnum.  In the shootings Mr. Ellifritz evaluated, 31% of those shot with a .22 did not stop, whereas only 9% of those shot with the .357 didn’t stop.  Does that prove that the higher energy round was the more effective stopper?  Yes indeed — as you’d expect.  But — I don’t think it proves it to be any more effective for psychological stops.  I think the .357 should obviously be expected to be a more potent physical incapacitator than the .22, and I think the “% that did not stop” field shows that perfectly well.  However, I think that same field also demonstrates the point I’m trying to make — those that DID stop from the .22, are more likely to have CHOSEN to stop.

Because the .22 is less likely to have caused the type of damage that forces someone to stop than the .357 is, it leaves the question open: then WHY did those who were shot just once by the .22, stop at all?

And the answer can only be — they were mainly psychological stops.

What about the .357 then — it had the same % of one-shot stops (61% vs. 60%) — can we say that it had the same percentage of psychological stops?  Again, I don’t think we can draw that conclusion from the data, because it’s clouded by the “% that did not stop” field.  I think a decent hypothesis would perhaps be — in any given group of people, regardless of what bullet they’re shot with, a certain percentage is predisposed to giving up right away.  Since all the categories showed generally similar one-shot-stop percentages (generally 47% to 61%), I think that is a hypothesis that, while unproven, could still reasonably be inferred.  However — what percentage of those who would have given up, were in fact instead incapacitated?  That may be the difference — if someone was forcefully incapacitated (as would be more likely from the more-damaging .357 bullet) then we can’t know whether they would have been a psychological stop or not, because the choice was taken away from them due to true incapacitation.  And that may be the answer we see, between the “% stopped after 1 shot” and “% that did not stop” fields.

So that brings us back to — does the higher energy transfer of a high-energy round like the .357 make it more likely to cause a psychological stop than a low-energy round?  While we don’t necessarily know, I think that if we stand the question on its head we can draw an inescapable conclusion — those who chose to stop psychologically, from the .22, weren’t doing so because of high energy transfer!  The .22 doesn’t have much energy to transfer, and its temporary cavity is positively tiny compared to the high-energy rounds like the .40 or .357.  And yet, 60% of those shot by the .22 either chose to stop, or were incapacitated (and, again, the likelihood of those who chose to stop would reasonably be higher for .22 than for the other calibers, because the likelihood of true physical incapacitation would be lower from the .22 as compared to the other calibers).  So if (hypothetically) high energy transfer is what causes someone to psychologically stop, then why would anyone who was shot with a .22 psychologically stop?  There’s no high energy to transfer!

Therefore, it seems safe to conclude that the level of energy transferred is likely not as significant a factor in causing a psychological stop as it may at first seem.

My guess?  Folks who have been shot get scared, and getting shot hurts, and seeing your blood leaking out of you hurts.  Plus we’ve been programmed by decades of Hollywood movies to “know” that just the very fact of getting shot means that you are supposed to drop on the ground and die right away.  Those factors all weigh on the psychology of someone who’s been shot, and I believe they are the contributing factors that cause a psychological stop, far more than the caliber of bullet or the amount of energy transferred by that bullet.  Accordingly, I don’t think that adding more energy or higher velocity is a good predictor for increasing the likelihood of a psychological stop.  Now, let’s back up and say — I think more energy, more power, bigger heavier bullets, and more shots on target are all good things — if you could do any one thing that would increase your likelihood of stopping an attack, I’d say more shots on target would be the most important thing.  But I’d always advise to carry the most powerful weapon that you can comfortably and accurately shoot.  Just because data has been correlated that show a .22LR has been able to cause 60% of the people shot by it to stop attacking, doesn’t mean it’s a good choice for self defense.  The more powerful the weapon, the bigger and deeper-penetrating the bullet, the more likelihood you have of causing a true incapacitating wound — and if you do that, then it takes all the guesswork, all the hypotheses, and all the questions and flings ’em right out the window.

First and foremost, place shots properly on the target to cause hits on the vital organs.  Second, place as many of those shots on target as you can until the attack stops.  Third, place them with the most powerful firearm that you can comfortably and accurately control.  Do that, and your likelihood of success in a defensive encounter will skyrocket, far more than worrying about whether your bullet transfers enough kinetic energy or what some one-shot-stop study says.


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15 thoughts on “What about Kinetic Energy Transfer? Does It Cause Psychological Stops?

  1. waldengr

    how do you have time to do all the testing, reading all the relevant research, write such compelling articles….and still have a normal job/life?

    this article should be posted to TTAG and other blogs. am about to barf at all the opinions that energy transfer is “stopping power”, opinons by people who just want everyone else to agree that the opiner’s favorite ammo is absolutely the best (because facts will not change their mind).

    once again, great stuff.

    probably a “duh” question, but have you looked at obtaining grants from gun manufacturers and LE agencies for your testing and research?


  2. Bill

    6 out of 7 people shot by a handgun will survive????? That is hogwash…. Survivability depends more on where you’re hit, and a lot of it depends on luck. If you really think survivability rates are that high, how do you explain the 4 police officers shot and killed by one deranged felon a few years ago in Lakewood WA. He killed 4 out of 4 people, and they all were treated by doctors ASAP. I’m sorry, but I’m not buying your claims on that….

    1. Shooting The Bull Post author

      They’re not my claims. I referenced the article wherein it was said, but I’ll link directly to the video where the statement was made:

  3. The Judge

    I think so many people survive handgun shots is because a lot of them are accidental shots wine carrying.

    If your gun touches one off accidentally while you are removing it from the holster, the shot you take to the foot will probably hurt, but you’ll probably survive.

    I don’t think the numbers tell the whole story in this case.

    I’d be curious to see how many intentional shooting victims survive, and compare it to the number of intentional long gun shooting victims who survive. I’m sure the long guns have a higher kill rate, but I bet the rates are much closer than the “6 out of 7 survive” would indicate.

  4. Jonathan Michael Langford

    I’m glad to see this discusion. I recently found a great reference for handgun wounding and effectiveness that highlights the exact topic of kinetic energy transfer. Specifically, it dismisses the possibility of remote wounding from handgun levels of energy . In summary, only a bullets penetration and permanent cavity should be considered.


  5. JimH

    The opinions of even folks with a scientific background are all over the map on this. I certainly started out many decades ago in the energy transfer camp, until one day an older friend introduced me to an even older man who had been shot 9 times with 8X57 Mauser in the torso – most of them were bad hits but one (according the scars he showed me) was a solid lung hit – close to the heart – and another was probably a borderline lung hit. This man killed the German machine-gunner who shot him and then sat down and passed out only to recover later in the aid station.

    One case doesn’t make a study, but it started me down the road of learning all I could. I tend to agree with scientists (they seem to fall into the rocket science field than the medical field but I know and respect folks in both). Those folks tell me that the sole effect of “energy transfer” (which falls under the laws of energy conservation and are part of Neton’s laws of thermodynamics) is to raise the temperature of the surrounding tissue – it is force (related to momentum) that does the damage… My college physics book told me that but at the time I didn’t believe it.

    Kinetic Energy converts directly to BTU s and Calories… a person undergoing laser surgery “absorbs” far more energy than a hit from a magnum revolver round. A good friend who is an MD (and has been a Military MD treating many gunshot wounds) and who by coincidence took part in the early US Rocket program while he was in grad school, tells me that you can “convert” as much Kinetic energy into “work” by eating a mini gummy bear as you would being shot with 11 .357 magnums – the point here is not that the .357 is ineffective but that looking at energy is the wrong direction to look.

    Mind you there aren’t really any mathematical models that predict the outcome of gunfights – as many point out not only is *what* you hit vitally important *who* you hit is even more so unless you happen to “scramble” the signals from the Central Nervous System (even if that is only temporary).

    Anyway good article, too many folks seem to think there is an easy answer – there isn’t.


    1. JimH

      I’m not quite sure I buy the 6 out of 7 figure, but at the same time I’m not doubting it, I’d have to look at the data used to come up with that. I actually think it is far higher – on average. But as someone else pointed out; averages don’t mean a thing – there are so many variables you have to factor in – placement and exactly what organ is damaged and to what degree it is damaged largely determines this, and believe it or not, mind set also does (old timers in the business remember a police officer who died instantly from an arm wound with a .25 auto – IIRC it is included in the Motorola training film all L.E. saw back in the day).

      A few months ago I was assisting with a class in a very large city and the Lead Instructor told the students (it was an Instructor class) that in that city the trauma center treated 3100 gunshot wounds the previous year (2013). Other hospitals in the are treated another 4 to 500 GSWs. Of those wounds, most of them were handgun wounds. Of those some 3500 cases there were only 100 fatalities.

      Now that doesn’t mean that only 1 in every 2500 or so people shot with a handgun die, after all, not all of the folks shot make it to the emergency room (at the same time there were only 200 homicides of any type in the city that year – 2013)

      I suspect the fact is we really don’t know. But I sure don’t find the most common figure I see – 9 out of 10 people shot with a handgun survive – to be unbelievable.

      The problem with statistics in this particular field is that too many folks who do not have a statistical background try to “analyze data” when the most important factors in causal relationships are not available to study. It doesn’t matter if Load X “works” (whatever that means) 90% of the time…what we need to know is will it work *this* time – and there are about 20 very important factors and 50 less important factors that will bear on the outcome… you cannot be confident of that likelihood based on the statistical analysis using available information, the “confidence interval” would be far too low.

      I stay in a state of perpetual confusion 😉


      1. Shooting The Bull Post author

        The “6 out of 7 survive” figure came from the youtube video of a doctor’s perspective on gunshots (which I’m sure you’ve seen).

        It’s entirely possible that the proper context might be “6 out of 7 of those who arrive at his hospital for treatment survive” (meaning, as you said, there are those who would be already expired prior to even being taken to a hospital). But, as you say, we don’t truly know. I don’t have any access to any comprehensive statistics on this, so I’m pointing out the one source that I did have (and hopefully have properly attributed it).

  6. Pete

    Did they look at the demographics of who was SHOOTING the .22LR Vs. other claibers in those one shot stops?

    I ask because reading your piece makes me think about my stereotypes who would be using the .22LR Vs a larger caliber. Shoot the largest caliber that you can shoot accurately, right? Those most likely to choose the .22LR, the infirm or elderly for example, might have appeared to the assailants as a weak and easier targets. I think that the surprise of simply encountering a gun in a victim demographic where it wouldn’t be “expected”, when combined with the realization that that “victim” was actually using the firearm, might account for this high one shop stop percentage. If the attacker knew going in, that he was going after what posed the likelihood of being a more hardened target, such as the stereotype of who would be carrying the .45 ACP, then he would probably already be more mentally geared against getting shot.

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  8. WCDUB

    I just can’t get around this notion:Of two projectiles,one heavy,one light,moving at the same velocity,fast or slow,the heavy one will have the greater impact.I would even go so far as to say that heavy moving slow has more impact than light moving fast.I just
    can’t think otherwise.Also,for me to believe that someone takes 17 CM shots of .40,or
    5 CM shots of .45,and keeps fighting,I have to believe that none of those shots hit any-
    thing vital.

    1. Shooting The Bull Post author

      You’re right, at the same speed, the heavier projectile will most definitely have the greater impact. And there’s a very good chance that the heavy/slow projectile would have more impact than a fast/light projectile.

      There are two ways to look at it; one is via kinetic energy, which is calculated as 1/2 * mass * velocity * velocity… and based on kinetic energy, one could argue that a fast/light 9mm is just as powerful as a slow/heavy .45. Example would be the Federal HST. In 9mm, the 124-grain +P version travels at 1200 fps, delivering 396 ft/lbs of energy. In .45 ACP, the standard-pressure 230-grain travels at 890 fps, delivering almost the same energy, 404 ft/lbs. But we’re talking about a bullet that’s almost twice as heavy — 230 grains is 1.855 times as heavy as 124 grains. It’s slower, yes, at 890 fps vs. 1200 fps. The formula for kinetic energy shows them as being basically comparable… But if you shoot them both at a steel target, you’ll hear a much louder, more solid thump from the .45 ACP.

      Kinetic energy is one thing, but there’s another very big factor, and that’s momentum. And momentum is calculated basically as mass * velocity; one formula that’s used frequently is the “power factor”, which is mass * velocity / 1000. Using that formula, the .45’s heavier bullet carries much more momentum than the 9mm does… the .45 HST has a power factor of almost 205, whereas the 9mm has a power factor of almost 149. That’s a pretty big difference — and that’s not even taking into account the .45 ACP +P version of the HST, which travels at 950 fps, delivers 461 ft/lbs of energy, and has a power factor of almost 219. So if we compare +P against +P, the .45 holds about a 16.4% advantage in kinetic energy, but almost 1.47x as much momentum.

      As to your second point, and whether anything vital was hit — definitely, vital organs were hit. They just didn’t result in an immediate stop. Hits in a lung or something like that may eventually cause death, but don’t necessarily immediately incapacitate the actor. Even in a direct heart shot, where the entire heart is completely destroyed, the person could retain enough residual oxygen in their system to be able to conduct voluntary movements for as much as 10 to 15 seconds — which can be an eternity when bullets are being exchanged.

      That’s one of the large differences between someone being “stopped” and someone being “killed”. The bullet may hit something vital and even eventually kill them, but the question is WHEN? Will it stop them before they can kill or seriously damage you? The primary interest we in the self-defense world have is in stopping the attacker, not in whether or not they get killed. The science says that the only way to guarantee an immediate stop is to hit the brain stem or upper spine. Short of that, the way to guarantee the most rapid incapacitation is to hit the circulatory system in a major blood-bearing organ such as the heart, aorta, or vena cava, because the bleedout from a major organ will rapidly cause unconsciousness. Other than that — there are no guarantees. You might destroy someone’s lung, their liver, their spleen, their stomach, any of these things might be a fatal shot, but they don’t necessarily guarantee that the person will stop right away. They will eventually stop, but the question is when?

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  10. Glen Mones

    As far as psychological trama causing some perp to stop ..according to Evan Marshall. Some studies suggest people cease ACTIONS 60% of the time when shot anywhere on the body ..with ANY CALIBER bullet ….the problem is the 40% that DONT..& if they are drunk ..or jacked up on drugs ..pcp what ever ..getting shot won’t mean anything to them ..so we have to depend on shot placement & loading 28th the most effective AMMO we can get ..


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