Velocity Versus Penetration

[TomJ]

In looking for a SD round, I settled on HST's. I am, however, a little confused about standard velocity versus +P. I've seen a number of gel tests where the +P penetrates less than the standard pressure round, 12 to 13 inches versus 15 with a 124 grain 9mm. My understanding, and please correct me if I'm wrong, is that the higher velocity of the +P causes it to expand quicker, leading to less penetration. My question is whether there's a benefit to the +P hitting at a higher speed that offsets the lower penetration? If not, is there a benefit to the +P?

 

[Kleanbore]

Regarding terminal ballistics only and ignoring "placement", penetration is key, followed by permanent wound channel.

Penetration depends upon velocity, mass, sectional density, bullet shape, and bullet construction.

I don't think you can separate out any one variable and make valid generalizations about it.

 

[jmr40]

If you are going to shoot them faster you need a tougher bullet that expands slower. Then you get the best of both.

 

[Steel Horse Rider]

I think that maybe you are leaving out the energy transferred to the target in your equation. Generally speaking if you have the same mass (bullet) traveling at a higher velocity (+P) you will have more available energy. As for penetration, you can use a FMJ bullet traveling at a specific velocity that may pass completely through the target mass where a flat nose or hollow point would only penetrate partially through the same target. More energy is transferred to the target with the latter. Imagine the movies, with more energy the bad guy is thrown backwards vs just standing there with hole in his chest. That is the answer to your question.

 

[bangswitch]

In looking for a SD round, I settled on HST's. I am, however, a little confused about standard velocity versus +P. I've seen a number of gel tests where the +P penetrates less than the standard pressure round, 12 to 13 inches versus 15 with a 124 grain 9mm. My understanding, and please correct me if I'm wrong, is that the higher velocity of the +P causes it to expand quicker, leading to less penetration. My question is whether there's a benefit to the +P hitting at a higher speed that offsets the lower penetration? If not, is there a benefit to the +P?

How far away do you plan to shoot in SD, and at what range are the gel tests done? A standard 9mm load (say, around 1000 fps) with 124 grain bullet will penetrate far enough to be lethal as far away as you could reasonably shoot accurately enough to place a round center mass. You only need to penetrate half of body thickness, less than 12 inches. Think of a +P as being a hot loaded standard round or a weak magnum. With higher MV, impact shock will be higher, even if penetration is more limited by the bullet design.

 

[Vern Humphrey]

Twelve inches is the FBI standard -- and is more than enough to shoot completely through the average male from any direction.

Handguns have relatively little energy (compared to rifles) so I wouldn't put too much reliance on "energy dump." I'd concentrate on making a big hole all the way through, and putting that hole in the right place.

 

[SDGlock23]

Assuming the gun even fires, placement is most important then penetration. Proper placement without sufficient penetration is bad and good penetration without proper placement isn't ideal either so you need both. What most refer to as "energy" is pretty much the least important of all, however with that said as long as it penetrates enough I'd lean towards the faster of the two because that will likely mean larger expansion.

 

[Al Thompson]

Think of a +P as being a hot loaded standard round or a weak magnum.

That may have been true 20 years ago, but I've noticed over the last five years or so that "+P" seems more about marketing and less about true velocity gains, at least going by the manufacturers reported velocities.

 

[mboylan]

I think that maybe you are leaving out the energy transferred to the target in your equation. Generally speaking if you have the same mass (bullet) traveling at a higher velocity (+P) you will have more available energy. As for penetration, you can use a FMJ bullet traveling at a specific velocity that may pass completely through the target mass where a flat nose or hollow point would only penetrate partially through the same target. More energy is transferred to the target with the latter. Imagine the movies, with more energy the bad guy is thrown backwards vs just standing there with hole in his chest. That is the answer to your question.

Energy is not a factor until you get into 1000-1200 fp or so. Common self defense rounds do not generate enough energy to generate hydrostatic shock or significant permanent cavitation. Nobody is thrown back by any bullet including very high powered rifle rounds. You are very much mistaken on all points.

 

[mboylan]

Twelve inches is the FBI standard -- and is more than enough to shoot completely through the average male from any direction.

Handguns have relatively little energy (compared to rifles) so I wouldn't put too much reliance on "energy dump." I'd concentrate on making a big hole all the way through, and putting that hole in the right place.

Also note that the FBI also uses very serious barrier penetration tests in addition to penetration in ballistic gel.

Twelve inches in ballistic gel does not equal twelve inches in a human body. You have to account for clothing including leather jackets, obstacles and bone. You have to account for the fact that most of the time a self defense shooting is at very close range with both you and your target moving. You will not get an unobstructed center of mass shot. People instinctively will hold up hands and arms in defense as well as turn various directions as they move. You will need to shoot through arms, hands and shoulders. Twelve inches of penetration in gel is not enough to bet your life on.

 

[Steel Horse Rider]

M: Thanks for the correction. It is good that on this site we have real experts.

 

[Frank Ettin]

....My understanding, and please correct me if I'm wrong, is that the higher velocity of the +P causes it to expand quicker, leading to less penetration. My question is whether there's a benefit to the +P hitting at a higher speed that offsets the lower penetration? If not, is there a benefit to the +P?...

As others have commented, "hitting at a higher speed (harder?)" isn't really a factor. Higher velocity generally means more reliable expansion, and a bigger hole is desirable.

There is a good deal of data, and there are studies, and we have some knowledge about wound physiology. What all that tells us 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.

• The goal is to stop the assailant.
  
  
• There are four ways in which shooting someone stops him:
  
  
  • psychological -- "I'm shot, it hurts, I don't want to get shot any more."
    
    
  • massive blood loss depriving the muscles and brain of oxygen and thus significantly impairing their ability to function
    
    
  • breaking major skeletal support structures
    
    
  • 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.
  
  
• With regard to the issue of psychological stops see
  
  
  • this study, entitled "An Alternate Look at Handgun Stopping Power" 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):

    ...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.
       
       
       • Considering the physiology of wounding, the data showing high incapacitation rates for light cartridges seems anomalous.
         
         
       • 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.
         
         
       • 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.
         
         
       • 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.
         
         
       • 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.
       
       
       • 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.
         
         
       • 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.
  
  
• 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....

• 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....

  
  
• 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....

 

[Steel Horse Rider]

My point of reference is the experience of my nephew as a special forces operator and the practice of head shots in eliminating a person from the fight. I have no "expert" published reports to post, only real experience.

 

[Jeff82]

Anecdotes can be used to prove anything as anything under the sun can happen once or a few times . The trick is finding general trends and using them to try to predict the performance of your tools.

 

[RustyShackelford]

defense caliber ballistics.....

I don't see anything wrong with +P or +P+ defense rounds for most calibers.
To me a handgun round should have a high muzzle vel; 1200-1400 FPS & a high KE level(kinetic energy) 450-600 ft/lbs. Calibers like .40Super, .357sig, 10mm, .357magnum, .40S&W, .38Super, etc.
As posted no common handgun round will be ideal or garentee 100%.

Frangibles & pre-fragmented brands like MagSafe, DRT, G2/RIP, TAP, Glaser Safety Slug, etc try to be the latest advancements in self defense/home security ammunition but many are not able to meet all their claims or perform like they state.
Frangibles can have some value(use in densely populated places or for back-ups/2nd guns).
As noted in the past, most back ups or 2nd guns used in a lethal force event will be at CQB ranges(0 to 6 feet). With the CCW holder/armed citizen facing the attacker.

 

[Nick Burkhardt]

Standard pressure/velocity JHP open up an average amount for good penetration.

+P pressure/velocity JHP open up an above average amount, are subject to more resistance in the body for lesser penetration.

 

[PowerG]

Shot placement and penetration. Everything else is incidental. Bullet expansion is nice, but doesn't happen every time. Frank Ettin's post above should be studied carefully. In many instances heavy-for-caliber bullets offer increased penetration over lighter bullet weights.

 

[TomJ]

Thanks for the info. I'll stick with the standard velocity, as the penetration is good and the reduced recoil helps with more accurate follow up shots.

 

[denton]

When a bullet strikes flesh, it produces a permanent wound channel and elastic stretching of the surrounding tissue. At low bullet speeds, more of the bullet energy goes into the permanent wound channel and little goes into elastic stretching of surrounding tissue. As bullet speed increases, less energy goes into the permanent channel, and more goes into the elastic stretching.

The force that a bullet exerts on tissue is the rate at which the bullet is shedding momentum. At some point, the bullet has shed enough momentum that the force per unit area (pressure) exerted by the bullet is less than the pressure required to crush tissue, and the bullet comes to rest. The longer the wound channel behind the bullet, the greater the chance that the bullet will intersect something that will deprive the target of blood and oxygen.

 

[Robert]

The op has made his desicion, let's stop while we are ahead.