Stopping power, true or fiction?

[g.willikers]

The ammo makers almost universally use ballistic gelatin as a measure of the effectiveness of ammunition.
And it's readily accepted as a guide, in choosing what we would use for self defense.
But should it?
The author of the article, a trauma surgeon who has seen, first hand, the results of many shootings, says maybe not.
And he says flesh and blood is very different from test media.
http://www.policemag.com/channel/wea...realities.aspx

[Madcap_Magician]

Ammo makers use ballistic gelatin testing as a proxy measure for the effectiveness of a bullet/load combination.

Ballistic gel is not an absolute indicator as to the actual performance of a particular load, but its virtue and the reason for its industry-wide acceptance is that it allows for a standard and objective comparison of different ammunition.

I don't see any ammunition manufacturers marketing gel testing as indicative of "stopping power," but I do see a lot of people on the gun boards who think they're the same thing.

[Dwight55]

You pose a good question, g. whillikers, . . . one that has befuddled, aggravated, and eluded us all for many a year.

No, . . . gelatin does not perfectly mimic the human torso. But, . . . yes, . . . it does a better job than a brick, cement block, 2 x 4, or a bathtub full of water.

The thing is with gelatin, . . . provided it is made consistently, . . . a level of comparison can be made between two rounds, . . . between power levels, . . . between bullet designs, . . . etc.

That, in effect, is what it really is, . . . a level playing field for comparison, and should never be taken as much more.

Inside the human torso, . . . you have bones, blood vessels, vital organs, muscles, . . . and each is different in size, proximity, angle of shot, etc. in each shooting incident, . . . making it almost impossible to get any real finite comparisons other than the blatantly obvious.

Gelatin will tell you that a 3 inch / 10 gauge slug probably will be a better one shot stopper than a .22 short. But, . . . that should have been obvious from the beginning.

Using gelatin to support the argument that a .45 caliber, 230 grain, BTHP is far superior to a .45 caliber, 220 grain hard cast lead slug, . . . just might be a stretch, . . . either way.

May God bless,
Dwight

[TailGator]

Yep, consistency is the key to good testing. Ballistic gel is valuable in eliminating variables. As said, the path of a bullet in a defensive shooting crosses multiple interfaces of cloth, skin, fat, muscle, and often bone. It is probably fair to say that no two bullets ever take the exact same path. Ballistic gel standardizes the bullet's path and resistance, so it makes for valid comparisons.

Quantifying stopping power itself would seem to be impossible because of the multiplicity of variables. Ballistic gel shows the potential for penetration and expansion of a round under ideal conditions. It is one factor for consideration, but not the only thing to think about. Real world results are also worth consideration, too, as long as part of your consideration is the realization that variables in the path, pain, psychological effects, vasculature, and so on are not controlled in such retrospective data.

[psalm7]

If one bullet design will expend its energy on impact and turn a area the size of a basket ball into " jelly " and another design will zip through and take most of the energy with it that shows what stopping power is . I know fmj's are leathal and bullet placment is critical and some times you will have to shoot throu cover but if I think there is a elevated chance of trouble I load performance ammo like Hydro shock hollow points .

[Frank Ettin]

Originally Posted by g.willikers

The ammo makers almost universally use ballistic gelatin as a measure of the effectiveness of ammunition.
And it's readily accepted as a guide, in choosing what we would use for self defense.
But should it?...

The thing is that ballistic gelatin is excellent for measuring what it measures -- the penetration and expansion of bullets in a homogenous "tissue like" medium. The preparation of ballistic gelatin for testing has also been standardized, so it is reasonably consistent. Using it as a test medium therefore allows meaningful comparison of the properties it measures, penetration and expansion, for various bullets in various cartridges.

But that is all it does. Ballistic gelatin test results do not absolute guarantee real world results. And there is no one test you can do today that can absolutely predict that one cartridge will give a better result than another when you get one shot at the guy charging you with a knife next Tuesday at 3:00 am.

Reliable information about penetration and expansion in "tissue like" media can be useful information when choosing a self defense cartridge. We just need to recognize that it's not definitive.

[g.willikers]

Has anyone done tests on cadavers, or large animal carcasses?
It's been done for archery, on deer and pigs.
The results there were as expected, the bow and arrow makers of the late medieval period knew what they were doing.
And what worked for them is still valid.
If it weren't for the restrictions on ammo design for the military, no doubt there would be plenty of studies on modern ammo.
But, as it stands, the only info available from the military is for "approved" ammo.
How about studies from police coroners, maybe?
Probably the best approach is to just rely on rapid fire accuracy, instead of the bullet.

[MoGas1341]

I'm going to have to agree with the doctor that wrote the article 100% Especially his closing statement ;
"... shot placement with any commercially available ammunition will offer you the best chance of maximizing your duty ammunition's stopping power."

There is another member on this forum that has a quote (and I'm paraphrasing here) 'I'd rather be shot in the foot with a .50 BMG than shot in the head with a .22LR' Which makes perfect sense to me.

Getting to my point, in my years of experience, I have NEVER seen a deer (even with a slug) get hit and literally be knocked to the ground by the force of the projectile. Shot placement through the heart definitely ensures that they don't go more than 50 yards or so but lets say the deer got hit in the gut by a 12 ga... It would probably run off and die a mile away by a horrible death, and all the while was never knocked to the ground. (This goes back to shot placement)

I apologize for the hunting comparison when the OP was discussing handgun defense ammo selection, but I don't feel that ballistic gelatin should be used as a guide for bullet effectiveness (much like how we select our hunting ammo)

[JD0x0]

Ballistic gelatin is good for what it's used for and that is creating a level playing field when comparing bullets. The thing is that the gelatin mainly mimics soft flesh and not muscle and bone so it doesn't show 'true' performance.

Due to the gel not having bones in it, it can make certain bullets look like they perform better than they will in a human or animal target.

For example, that extremely gimmicky R.I.P. round.
http://g2rip.com/

In gelatin, this bullet almost looks like it could perform well. The thing is, gel is soft, and those little shreds that strip off the bullet as shrapnel, will travel through the gel pretty well. The down side is, if you were to use these bullets for their intended SD purposes, and you shot someone in the chest, chances are all those pieces would breakoff and stop when they hit the ribs, not really doing much damage.

In reality a dead pig would probably be a better test for bullet performance in humans, the problem is every pig is different, so you cant get 100% consistent results, when testing different rounds. The gel serves it's purpose fine, but it will not prove performance on game or humans for SD.

[Frank Ettin]

Originally Posted by g.willikers

...Probably the best approach is to just rely on rapid fire accuracy, instead of the bullet.

Sigh...

There is data, and there are studies, and we have a good deal of knowledge about wound physiology. But we keep getting into these "ring-around-the-rosie" discussions because, I guess, a lot of people are dissatisfied that there really is no definitive answer.

Perhaps the real conclusion(s) with regard to self defense could be summarized as follows:

1. Pretty much every cartridge ever made has at times succeeded at quickly stopping an assailant.
   
   
2. Pretty much every cartridge ever made has at times failed at quickly stopping an assailant.
   
   
3. Considering ballistic gelatin performance, data available on real world incidents, an understanding of wound physiology and psychology, certain cartridges with certain bullets are more likely to be more effective more of the time.
   
   
4. For defensive use in a handgun the 9mm Luger, .38 Special +P, .40 S&W, .45 ACP, .357 Magnum, and other, similar cartridges when of high quality manufacture, and loaded with expanding bullets appropriately designed for their respective velocities to both expand and penetrate adequately, are reasonably good choices.
   
   
5. And that's probably as good as we can do.

I've posted the following before and might as well post it again here:

Let's consider how shooting someone will actually cause him to stop what he's doing.

1. The goal is to stop the assailant.
   
   
2. There are four ways in which shooting someone stops him:
   
   
   1. psychological -- "I'm shot, it hurts, I don't want to get shot any more."
      
      
   2. massive blood loss depriving the muscles and brain of oxygen and thus significantly impairing their ability to function
      
      
   3. breaking major skeletal support structures
      
      
   4. damaging the central nervous system.
   
   Depending on someone just giving up because he's been shot is iffy. Probably most fights are stopped that way, but some aren't; and there are no guarantees.
   
   Breaking major skeletal structures can quickly impair mobility. But if the assailant has a gun, he can still shoot. And it will take a reasonably powerful round to reliably penetrate and break a large bone, like the pelvis.
   
   Hits to the central nervous system are sure and quick, but the CNS presents a small and uncertain target. And sometimes significant penetration will be needed to reach it.
   
   The most common and sure physiological way in which shooting someone stops him is blood loss -- depriving the brain and muscles of oxygen and nutrients, thus impairing the ability of the brain and muscles to function. Blood loss is facilitated by (1) large holes causing tissue damage; (2) getting the holes in the right places to damage major blood vessels or blood bearing organs; and (3) adequate penetration to get those holes into the blood vessels and organs which are fairly deep in the body. The problem is that blood loss takes time. People have continued to fight effectively when gravely, even mortally, wounded. So things that can speed up blood loss, more holes, bigger holes, better placed holes, etc., help.
   
   So as a rule of thumb --
   
   
   • More holes are better than fewer holes.
     
     
   • Larger holes are better than smaller holes.
     
     
   • Holes in the right places are better than holes in the wrong places.
     
     
   • Holes that are deep enough are better than holes that aren't.
     
     
   • There are no magic bullets.
     
     
   • There are no guarantees.
   
   
3. With regard to the issue of psychological stops see
   
   
   1. this study by Greg Ellifritz. And take special notice of his data on failure to incapacitate rates:
      
      

      

      
      As Ellifritz notes in his discussion of his "failure to incapacitate" data (emphasis added):

      Originally Posted by Greg Ellifritz

      
      ...Take a look at two numbers: the percentage of people who did not stop (no matter how many rounds were fired into them) and the one-shot-stop percentage. The lower caliber rounds (.22, .25, .32) had a failure rate that was roughly double that of the higher caliber rounds. The one-shot-stop percentage (where I considered all hits, anywhere on the body) trended generally higher as the round gets more powerful. This tells us a couple of things...
      
      In a certain (fairly high) percentage of shootings, people stop their aggressive actions after being hit with one round regardless of caliber or shot placement. These people are likely NOT physically incapacitated by the bullet. They just don't want to be shot anymore and give up! Call it a psychological stop if you will. Any bullet or caliber combination will likely yield similar results in those cases. And fortunately for us, there are a lot of these "psychological stops" occurring. The problem we have is when we don't get a psychological stop. If our attacker fights through the pain and continues to victimize us, we might want a round that causes the most damage possible. In essence, we are relying on a "physical stop" rather than a "psychological" one. In order to physically force someone to stop their violent actions we need to either hit him in the Central Nervous System (brain or upper spine) or cause enough bleeding that he becomes unconscious. The more powerful rounds look to be better at doing this....

      1. There are two sets of data in the Ellifritz study: incapacitation and failure to incapacitate. They present some contradictions.
         
         
         1. Considering the physiology of wounding, the data showing high incapacitation rates for light cartridges seems anomalous.
            
            
         2. Furthermore, those same light cartridges which show high rates of incapacitation also show high rates of failures to incapacitate. In addition, heavier cartridges which show incapacitation rates comparable to the lighter cartridges nonetheless show lower failure to incapacitate rates.
            
            
         3. And note that the failure to incapacitate rates of the 9mm Luger, .40 S&W, .45 ACP, and .44 Magnum were comparable to each other.
            
            
         4. If the point of the exercise is to help choose cartridges best suited to self defense application, it would be helpful to resolve those contradictions.
            
            
         5. A way to try to resolve those contradictions is to better understand the mechanism(s) by which someone who has been shot is caused to stop what he is doing.
         
         
      2. The two data sets and the apparent contradiction between them (and as Ellifritz wrote) thus strongly suggest that there are two mechanisms by which someone who has been shot will be caused to stop what he is doing.
         
         
         1. One mechanism is psychological. This was alluded to by both Ellifritz and FBI agent and firearms instructor Urey Patrick. Sometimes the mere fact of being shot will cause someone to stop. When this is the stopping mechanism, the cartridge used really doesn't matter. One stops because his mind tells him to because he's been shot, not because of the amount of damage the wound has done to his body.
            
            
         2. The other mechanism is physiological. If the body suffers sufficient damage, the person will be forced to stop what he is doing because he will be physiologically incapable of continuing. Heavier cartridges with large bullets making bigger holes are more likely to cause more damage to the body than lighter cartridges. Therefore, if the stopping mechanism is physiological, lighter cartridges are more likely to fail to incapacitate.
         
         
      3. And in looking at any population of persons who were shot and therefore stopped what they were doing, we could expect that some stopped for psychological reasons. We could also expect others would not be stopped psychologically and would not stop until they were forced to because their bodies became physiologically incapable of continuing.
         
         
      4. From that perspective, the failure to incapacitate data is probably more important. That essentially tells us that when Plan A (a psychological stop) fails, we must rely on Plan B (a physiological stop) to save our bacon; and a heavier cartridge would have a lower [Plan B] failure rate.
   
   
4. Also see the FBI paper entitled "Handgun Wounding Factors and Effectiveness", by Urey W. Patrick. Agent Patrick, for example, notes on page 8:

   ...Psychological factors are probably the most important relative to achieving rapid incapacitation from a gunshot wound to the torso. Awareness of the injury..., fear of injury, fear of death, blood or pain; intimidation by the weapon or the act of being shot; or the simple desire to quit can all lead to rapid incapacitation even from minor wounds. However, psychological factors are also the primary cause of incapacitation failures.
   
   The individual may be unaware of the wound and thus have no stimuli to force a reaction. Strong will, survival instinct, or sheer emotion such as rage or hate can keep a grievously wounded individual fighting....

5. And for some more insight into wound physiology and "stopping power":
   
   
   • Dr. V. J. M. DiMaio (DiMaio, V. J. M., M. D., Gunshot Wounds, Elsevier Science Publishing Company, 1987, pg. 42, as quoted in In Defense of Self and Others..., Patrick, Urey W. and Hall, John C., Carolina Academic Press, 2010, pg. 83):

     In the case of low velocity missles, e. g., pistol bullets, the bullet produces a direct path of destruction with very little lateral extension within the surrounding tissue. Only a small temporary cavity is produced. To cause significant injuries to a structure, a pistol bullet must strike that structure directly. The amount of kinetic energy lost in the tissue by a pistol bullet is insufficient to cause the remote injuries produced by a high-velocity rifle bullet.

   • And further in In Defense of Self and Others... (pp. 83-84, emphasis in original):

     The tissue disruption caused by a handgun bullet is limited to two mechanisms. The first or crush mechanism is the hole that the bullet makes passing through the tissue. The second or stretch mechanism is the temporary wound cavity formed by the tissue being driven outward in a radial direction away from the path of the bullet. Of the two, the crush mechanism is the only handgun wounding mechanism that damages tissue. To cause significant injuries to a structure within the body using a handgun, the bullet must penetrate the structure.

   • And further in In Defense of Self and Others... (pp. 95-96, emphasis in original):

     Kinetic energy does not wound. Temporary cavity does not wound. The much-discussed "shock" of bullet impact is a fable....The critical element in wounding effectiveness is penetration. The bullet must pass through the large blood-bearing organs and be of sufficient diameter to promote rapid bleeding....Given durable and reliable penetration, the only way to increase bullet effectiveness is to increase the severity of the wound by increasing the size of the hole made by the bullet....

   
   
6. And sometimes a .357 Magnum doesn't work all that well. LAPD Officer Stacy Lim who was shot in the chest with a .357 Magnum and still ran down her attacker, returned fire, killed him, survived, and ultimately was able to return to duty. She was off duty and heading home after a softball game and a brief stop at the station to check her work assignment. According to the article I linked to:

   ... The bullet ravaged her upper body when it nicked the lower portion of her heart, damaged her liver, destroyed her spleen, and exited through the center of her back, still with enough energy to penetrate her vehicle door, where it was later found....

[Double Naught Spy]

Has anyone done tests on cadavers, or large animal carcasses?

Yes.

How about studies from police coroners, maybe?

Yes.

Just like with the arrow examples you noted above, not all arrows worked all the time depending on the angles hit, bones hit, tissues, hit, etc. Same for bullets.

The one thing arrow makers testing carcasses have found out just like the bullet folks is that shooting dead things always produces a stop and shooting live things does not.

Funny article. The guy wants "stopping power" dropped from use but then continues to use the phrase in the article and even offering what should be the correct definition of it, LOL, and that definition being rather vague, covering two of the suggested possibilities listed.

Strange that as a doctor, he has failed to note that ammunition, like medicines or medical treatments, doesn't also work of a given individual in a given manner. He can't tell me that my broken leg will heal in XX.xx days or exactly how well my leg will feel in XX.xx days, despite being a surgeon. He can't tell me how much pain reliever is needed to relieve my pain sufficiently despite countless studies in that area of medicine.

If human bodies were 100% uniform with one another and people getting shot were getting shot in 100% uniform manners with 100% uniform ammunition, etc., then we could expect 100% uniform results, but still would not get them. However, human bodies are not 100% uniform. People's attitudes and behaviors under stress and in responding to stress are not uniform. When people get shot, they don't get shot in a uniform manner to everyone else either.

The problem isn't so much with using ballistic gelatin as it is with the combinations and permutations of variables that influence whether a given person being shot will be stopped or will not be stopped. These certainly include but are not limited to ballistics, bullet construction, velocity at impact (relates to shooting distances), angle of entry, trajectory through the body, health of the individual, size and shape of the individual, mindset of the individual, etc.

As we have seen all too many times, the difference between life and death can come down to mere fractions of an inch and so mere fractions of an inch difference can be what influences differences in performance. When Doc Vail can control for all these combinations and permutations, then maybe we should consider revisiting whether or not gel testing is valid or not.

{I see Frank's and my posts overlapped. His answer is probably much better}

[jmr40]

There is no perfect way to predict what will happen. Lots of studies have been done, using lots of methods. The ballistic gel tests, while not perfect, are probably the most reliable way to predict what will happen.

[pathdoc]

Gelatin allows a like-with-like comparison, inasmuch as the test conditions can be standardised across all ammo tested. Anyone wishing to question the findings can reproduce the test conditions exactly and publish their own conclusions.

It removes many of the variables and gives a general (usually an optimum) indication of how an expanding bullet will behave, and with sufficiently high film speeds or frame rates can allow analysis of how those expanding noses actually work and whether they do exactly what the designer intended them to do.

The last controlled human tests that I know of in any democratic nation were conducted at the turn of the 20th Century, and were performed on the cadavers of executed criminals. Not long after this, the Hague Convention outlawed expanding smallarms ammo and the point became moot.

The best we have now is the uncontrolled tests which are the accounts of law-enforcement officers and armed civilians acting in defence of themselves and others. Unfortunately, due to the nature of the encounters, these are at best collections of anecdotes and not the ideal, standardised data we would love to have. Trying to draw conclusions from them is fraught with hazard, and anyone doing so had better admit the limitations of their study up-front.

[Bultaco]

Stopping power is pretty much a useless term that gets used by people with low info on defensive shooting. Stopping what? 100 lb. granny or 280lb. PCP freak.
The FBI testing added performance through normally encountered barriers. Cloth, sheet rock steel & glass. Nothing can be definitive on a subject with that many variables. At least FBI protocol gives you some idea how the bullet may perform after these barriers. Bones can't be done consistently so they will have to remain one of the millions of variables.
Many people want to believe that they have THE answer to the ammo question. They should spend the time working on their skill that they do talking about the unknowable.

[Deaf Smith]

Stopping power, true or fiction?

Just looking at autopsy can be very misleading due to one not knowing the facts of the shooting. That is how long they stayed on their feet once wounded.

Stopping power has SOME truth in it.

Morgue monsters, those who visit the autopsy as well as interview the cops and citizens who used the guns to stop the bad guys have found that larger more powerful rounds DO TEND to stop better.

Massad Ayoob, Marshal, Sanow, and others.

More powerful rounds like .357 Magnum, .40 S&W, .45 ACP, DO TEND to stop better.

Rounds with JHP and SWCHP designs DO TEND to stop better.

When shots are placed in very vital areas they DO TEND to stop better.

David Spauling once wrote that after viewing a very large number of surveillance videos that caught shootouts that you could see a more definite reaction to the ones shot with larger more powerful rounds.

So with all that said the wises choice is to find a gun/ammo combination that is the most powerful one you can control and hit accurately and still carry daily.

And that advice goes back way before even Col. Jeff Cooper.

Deaf

[James K]

"Stopping power" and "knockdown power" are mostly fictional. Some will contend that a .45 will "knock a man off his feet", or "stop a charging bull in its tracks."

Well, here is a thought. During the Civil War, Confederate General Leonidas K. Polk was shot while observing the enemy. According to one eyewitness, he was not knocked down, but stood for a few seconds and then fell.

The weapon was a 20 pdr. Parrott rifle; the projectile was 3 2/3 inches in diameter and weighed around 140,000 grains, just a bit bigger than a .45 ACP bullet.

Jim

[Derbel McDillet]

The most relevant statement in Dr. Vail's article:

But does this ammunition have acceptable stopping power? Only if it hits a vital structure that would "stop" the target from continuing the fight.

The most ignorant statement in Dr. Vail's article:

When ammunition companies or regulatory agencies begin to use computer simulations, simulant tests, animal models, autopsy results, and trauma surgeon operation reports with hospital summaries to determine the effectiveness of their products, then we will know which ammunition can be labeled as having the "best stopping power." And this claim will be based on scientific data rather than incomplete ballistic testing.

Dr. Martin Fackler, who developed the 10% ordnance gelatin solution commonly used today to test ammunition terminal performance and wounding effects, has repeatedly stated that the street is the ultimate laboratory. The wound profiles produced in properly prepared and calibrated ordnance gelatin have been verified and validated against thousands of actual shootings.

Unfortunately Dr. Vail doesn't provide any data to backup his statement.

The primary measure of "stopping power" is the amount of permanent damage produced by a bullet. Properly prepared and calibrated 10% ordnance gelatin provides a REASONABLE MEASURE of terminal performance and wounding effects.

[Deaf Smith]

Dr. Martin Fackler, who developed the 10% ordnance gelatin solution commonly used today to test ammunition terminal performance and wounding effects, has repeatedly stated that the street is the ultimate laboratory. The wound profiles produced in properly prepared and calibrated ordnance gelatin have been verified and validated against thousands of actual shootings.

And that is what the morgue monsters found. Autopsy does not show how it did in the street cause all a autopsy is good for is DEAD PEOPLE.

Most people survive gun shots. Hint hint....

The police reports of the incidents matter so much more cause alot of them were shot, stopped, but still lived.

Well, here is a thought. During the Civil War, Confederate General Leonidas K. Polk was shot while observing the enemy. According to one eyewitness, he was not knocked down, but stood for a few seconds and then fell.

The weapon was a 20 pdr. Parrott rifle; the projectile was 3 2/3 inches in diameter and weighed around 140,000 grains, just a bit bigger than a .45 ACP bullet.

Well yes but a certain James Butler Hickok killed an adversary at 75 yards with one shot from a .36 Navy Colt. And later he faced five men in a barn and killed all five with those .36 Navy Colts. He had real good shot placement.

There are freak incidences where people have survived crowbars blown through their heads to. But in GENERAL, larger diameter cartridges tend to stop better. More powerful rounds tend to stop better. And more precise shot placement tends to stop better.

But just case a Parrott cannon ball didn't stop one person, or a puny .36 Navy Colt drop'em dead, does not mean stopping power does not exist.

Deaf

[Colt46]

The only thing that you can really count on is that bullets don't get smaller when they hit the target.
Terms like 'stopping power' and 'knockdown power' are interesting concepts but how do you base any meaningful numbers around them?

[zombietactics]

I'm just going to weigh in with a 99% agreement with Frank Ettin's post and (mostly/maybe/hopefully) leave it at that.

It's an interesting discussion, provided all of the parties involved are interested in a rational discussion. It's been my experience that many (most?) are not, and simply wish to hawk/hype for the gun/caliber/brand they prefer, absent any objective reason or evidence.

As irritating as that can be, this still amounts to arguing about angels dancing on the head of a pin. If you choose a quality, duty-rated round, verify it works reliably in your gun(s), AND train/practice enough to be reasonably proficient ... that's where the line twixt life and death is drawn.

[Double Naught Spy]

The only thing that you can really count on is that bullets don't get smaller when they hit the target.

Actually, some do, and were designed to do so.

[dayman]

There are four ways in which shooting someone stops him:

I. psychological -- "I'm shot, it hurts, I don't want to get shot any more."

II. massive blood loss depriving the muscles and brain of oxygen and thus significantly impairing their ability to function

IV. breaking major skeletal support structures

V. damaging the central nervous system.

I agree with the above, except that passing out from shock should be put somewhere in there.
I'm not sure if it would be psychological or physiological, but a person's body can shut itself down before blood loss forces it, and without a conscious "ouch that hurts" decision. Think TKO from body shots in a boxing match.

Not that it's particularly helpful though, as what will send a person into shock is probably even more variable than terminal ballistics.

[zombietactics]

In this context "shock" is generally defined as lack of perfusion of blood to vital organs like the brain.

As such, shock is one effect of massive blood loss ... especially when it results in a drop of blood pressure.

So, item "II" above: "... massive blood loss depriving the muscles and brain of oxygen and thus significantly impairing their ability to function ..." pretty much covers that.

[Frank Ettin]

The term "shock" is also sometimes used to refer to "acute stress reaction", a psychological response to extreme trauma.

[Mike1234]

I doubt anyone here would disagree that a .50 BMG shot to the middle torso has a much better chance of immediately incapacitating an assailant than a .22 LR shot at precisely the same spot. The question that remains is how much difference is there in the calibers in between? Or how about a tank mortar round to the torso?

I choose to balance "damage per shot" with "number of shots available". My HD pistol is a 9mm 18+1 with Federal HST cartridges. My HD shotgun is a semi-auto 12ga with 8+1 rounds of #4 buckshot.