overpenetration and "expending energy in the target"?

[hardheart]

Why is overpenetration considered bad in damaging a target? This is NOT about legal ramifications or collateral damage. I understand those concerns perfectly well and find them valid. What I do wonder about is the criticism of rounds that pass through a target, in that it is considered that not enough damage is then done. Now, if it is an expanding round and it does not do so while passing through, then yes, not enough damage is done. But take two other cases.

A non-expanding FMJ pistol round. It is not going to deform or fragment. If it stops in the body, then the wound track is going to stop with it. The deeper the penetration, all the way to pass-through, the longer the wound track. The track isn't going to get larger in diameter, the bullet doesn't deform to do so. The temporary cavity is going to be affected by velocity, so heavier and faster will get you better penetration and higher impact energies. If what you want to do is damage as much of the target as possible, then you should be reaching as deep as possible, all the way through.

An expanding pistol round. This is actually no different from FMJ in this regard. By expanding, the round deforms, creating a larger permanent cavity and 'applying the brakes'. Again, stopping in the body to prevent striking unintended targets is a good thing for other reasons. But, I don't see the "maximum energy transfer" argument for wanting the bullet to stop in the middle. Again, the deeper the wound track, the more tissue damaged. The expanding round now gives you a larger and longer wound track with full pass through. The energy transfer is seen in the displaced and destroyed tissue, not in where the bullet stops. If the bullet stops in the target, it just means it had less energy than one that passes through in the same condition.

Am I wrong in my supposition that purely for wounding potential, a bullet that both expands and penetrates completely through the target is the best option?

 

[Eric M]

A simple pass through is not going to give you the same magnitude of wounding that something like a fragmenting rifle round will. I recall from a dissertation on bullet wounds by a surgeon that was posted here that there is not much they can do for rifle wounds while most times a pistol round can be patched up pretty easily.

 

[Shadow 7D]

kinda, except that few pistols will provide the energy needed to drive the expanded round through and through.

the point is, you gotta touch it to matter, expanding (once adequate penetration is achieved) lets your round 'touch' more. A HP is designed to stop in the target as they are usually used by Police, and NOT getting a through and through is pretty high on their books.

 

[481]

Why is overpenetration considered bad in damaging a target? This is NOT about legal ramifications or collateral damage. I understand those concerns perfectly well and find them valid. What I do wonder about is the criticism of rounds that pass through a target, in that it is considered that not enough damage is then done. Now, if it is an expanding round and it does not do so while passing through, then yes, not enough damage is done. But take two other cases.

A non-expanding FMJ pistol round. It is not going to deform or fragment. If it stops in the body, then the wound track is going to stop with it. The deeper the penetration, all the way to pass-through, the longer the wound track. The track isn't going to get larger in diameter, the bullet doesn't deform to do so. The temporary cavity is going to be affected by velocity, so heavier and faster will get you better penetration and higher impact energies. If what you want to do is damage as much of the target as possible, then you should be reaching as deep as possible, all the way through.

An expanding pistol round. This is actually no different from FMJ in this regard. By expanding, the round deforms, creating a larger permanent cavity and 'applying the brakes'. Again, stopping in the body to prevent striking unintended targets is a good thing for other reasons. But, I don't see the "maximum energy transfer" argument for wanting the bullet to stop in the middle. Again, the deeper the wound track, the more tissue damaged. The expanding round now gives you a larger and longer wound track with full pass through. The energy transfer is seen in the displaced and destroyed tissue, not in where the bullet stops. If the bullet stops in the target, it just means it had less energy than one that passes through in the same condition.

Am I wrong in my supposition that purely for wounding potential, a bullet that both expands and penetrates completely through the target is the best option?

I don't think so.

As with anything there is a balance to be struck. You can have a JHP that expands to the diameter of a hubcap that will penetrate to a depth of only a few inches; you can have a JHP that barely expands at all and will punch through even the largest assailant with plenty of gas to spare. Somewhere in between lies the answer.

The FBI test protocols specifiy a round that'll expand regardless of barrier and still penetrate somewhere between 12 and 18 inches- probably the best "overall" balance there is.

 

[BADUNAME37]

Bang-Flop-Drop

If the bullet expands and does go all the way through, but if the velocity of the projectile at exit is nearly nothing, then we can assume that the MAJORITY of energy was expelled within the target.

I shot a black bear in the neck with a Hornady 270 Win 130g Soft Point Spire bullet. The bullet expanded and the energy and speed of the bullet created a large hollow cavity inside the bear's neck the size of a man's fist, as well as taking out and 'vaporizing' several vertebrae before exiting from a very small hole on the other side of the roughly 10" diameter neck. It would be safe to say that the MAJORITY of energy was expended inside the bear's neck. Coming out, the bullet may have had as much power as a BB gun, maybe more, maybe less.

To put it simply, it was a "bang-flop-drop" type of shot, the major reason it was such a clean kill was due to the fact that the distance the bear was from me was approximately 40 feet -- enabling me to take a well-aimed, well-placed shot at the base of the brain.

The advantage I had was my extremely close distance thus being able to take an extremely-accurate and deadly shot.

Things might have played-out differently had that bear been 150 yards away! I might not have broken his neck, and I might not have even found him after the shot, making me wonder if I really, in fact, even hit him!

Had I used a FMJ projectile, the exit wound and the ENTIRE wound channel would all most likely would have been extremely narrow, compared to the wound I created using the bullets I used! However, there again, my advantage was my extremely close distance from him, I could have shot him in the head with a FMJ at the distance I was standing when I first saw him pop his head above the black raspberries! His head and neck were really all I could see, as I instantly had him in my crosshairs!

 

[easyg]

Some folks don't believe energy matters, and some do believe it matters.
But I do know this...
Rounds like the 9mm Para had no problem penetrating completely through the average human when in FMJ, but it is also a notoriously poor "man stopper" in FMJ.
But the 9mm Para in hollow-point, with its more limited penetration, performs much better.

 

[Shadow 7D]

It's kinda like comparing cars and trucks, I can have a HUGE dumptruck with 500HP engine, that is a VERY poor performer, or a Geo Metro with a 200 HP engine that can get to a VERY high speed, but has 'issues' getting there.

Balisticians try to build the best tradeoff, one that penetrates (looking at barriers for 9mm and heavier) expands but keeps mass and still is accurate. Ideally, you would have a round that expands to the size of a hubcap and stops exactly at 12"-18" (depending on your school)

 

[JShirley]

I am concerned about not endangering innocent lives in my quest to protect my own life and the lives of those I love. That's my most important reason for using a rapidly expanding and/or fragmenting round.

I don't care so much about "energy dump" or what whatnot, as I want to make a large hole in the target. Bullets that rapidly expand after hitting the target not only make a much larger hole, but also meet my (defensive) goal of not being very dangerous if they penetrate all the way through, since most of their forward energy has already been expended.

I don't think you're using overpenetration in the sense most of us use it. Overpenetration is more penetration than desired. If you're hunting game, typically you want both entrance and exit wounds. Since this is the goal, this performance is not overpenetration. On the other hand, if you were shooting defensively, and used 00 buck at close range, and 1 of the pellets went through the home invader and killed your 3 year old in the next room, that would be overpenetration. Just as shooting an attacker with 9x19mm FMJ and killing your 3 year old and the 5 year old in the room past that.

John

 

[hardheart]

Thank you for the responses so far, I will try to address some and maybe clarify my thinking a bit more.

A simple pass through is not going to give you the same magnitude of wounding that something like a fragmenting rifle round will.

I agree. I would like to mention, and failed to do so initially, that I was focusing on handguns. Additionally, I would like to revisit mom-fragmenting fmj. The simple pass-through is less wounding than fragmenting, but also, isn't the pass-through more wounding than an fmj round that stopped in the target? Also, wouldn't fragments that pass-through be more wounding than fragments that stay in the target? This is what I am thinking most about, that no matter the projectile actions inside the target, if they undertake any particular kind of shape change, then a pass-through after that is an increase in wounding.

kinda, except that few pistols will provide the energy needed to drive the expanded round through and through.

the point is, you gotta touch it to matter, expanding (once adequate penetration is achieved) lets your round 'touch' more

True, pistols are limited, and I understand the trade-off necessary due to limited case capacity and barrel length. I will point to a later comment in what I think I am seeing, though could just be reading things wrong. And I agree that expanding damages more tissue, but I would say so does deeper penetration. The trade-off for safety purposes would be expansion and less penetration. I don't quite see why that trade-off is preferable just for damaging the target. I don't want to get into shot placement, but the service calibers aren't all that huge, even when expanded. What an fmj touches and what a jhp touches aren't going to be orders of magnitude apart in volume.

The FBI test protocols specifiy a round that'll expand regardless of barrier and still penetrate somewhere between 12 and 18 inches- probably the best "overall" balance there is.

I get the minimum of 12 inches for adequate qounding, and I think the 18 is again not for wounding the intended target, but for safety of others. That's where I am looking. I could be completely wrong, but after reading many, many posts on many boards, it seems there are at least a few people who think that the bullet has to stop inside the target. Not to stop for safety and unintended damage, but because if it doesn't stop, then the target won't go down. I would like to highlight that I mean greater penetration for the same diameter. FMJ stopping in the target or fmj passing through, the bullet looking almost good enough to reload. Also, a magic jhp that can be loaded to penetrate 15" and expand to 200%, or that jhp penetrating 30" and still expanding to 200%. Does anyone think that the jhp penetrating to 30" is actually less likely to drop the target?

If the bullet expands and does go all the way through, but if the velocity of the projectile at exit is nearly nothing, then we can assume that the MAJORITY of energy was expelled within the target.

True, and this would be a candidate for my idea of a super bullet. Full penetration, but 'smart' in that it can't injure anything else upon exit. The next level would be a round that fragments, and the fragments take a scenic tour of the internals before exiting in the same manner and falling out of the target by gravity alone.

I don't think 'expelling' the energy is important to wounding, only to prevention of creating secondary targets. Just because the round has some velocity upon exit does not instantly mean there was no tissue damage in the target. The obvious example of this are solid rifle rounds that exit. Those monolithic rounds that blow through African game still make them dead. Of course the velocity levels are different, but then doesn't that mean momentum and energy numebrs are important, and that "dumping" all of the energy into the target and not exiting are not important for terminal ballistics solely for wounding.

Rounds like the 9mm Para had no problem penetrating completely through the average human when in FMJ, but it is also a notoriously poor "man stopper" in FMJ.
But the 9mm Para in hollow-point, with its more limited penetration, performs much better.

This is one I would like to look at a bit. To me, it seems the statement is "pass-through = poor man-stopper, limited penetration = man-stopper". Now, is this accurate? If a non-expanding 12 ga. slug passes through the target, does that mean it will not stop the target (if it's a man?) If the slug dis stop in the target, does that increase its performance? If 9mm fmj did not pass through, does that make it wound more effectively than fmj that does pass through? Or, is it that the volume of the wound track of the expanded 9mm is greater than the wound track of the non-expanded pass-through? If so, then would an expanded 9mm with pass-through equal an even greater volume wound track, and thereby even better terminal performance? If we go back to my magic bullet, 200% expansion with full penetration, and make it a 9mm. Well, that would be a smidge over 0.7" permanent wound track all the way through. Isn't that almost the same diameter as a 12 gauge slug?

Ideally, you would have a round that expands to the size of a hubcap and stops exactly at 12"-18" (depending on your school)

I think expansion is very important, as it means we have the bullet travel through air with minimal resistance, yet travel through the target with high resistance, transferring more energy to more tissue. But, is the 12-18" the exact penetration, or the minimum penetration? If it is exact, I would think that only for the safety factor to protect others.

I don't think you're using overpenetration in the sense most of us use it. Overpenetration is more penetration than desired. If you're hunting game, typically you want both entrance and exit wounds. Since this is the goal, this performance is not overpenetration.

I am still using it in the same sense, just trying to address something that may or may not actually be there. That is, that pass-through isn't just dangerous for others, but that it means the wounding of the intended target actually suffers.

almost all the comments I see about wanting the round to stop in the target are about safety, and I want to emphasize I take no issue with that at all. I have seen some comments though that say roughly "I want the round to stop in the target to maximize energy dump and do the most damage" That is the rough statement I think I am seeing that makes me wonder exactly what they are communicating.

Sorry for the lengthy post.

 

[Vern Humphrey]

Am I wrong in my supposition that purely for wounding potential, a bullet that both expands and penetrates completely through the target is the best option?

Not at all. For one thing, a bullet that penetrates completely in the ideal situation is one that will penetrate deeper when the situation is less than ideal.

And for another, there are things a bullet hits on the way out that are as disabling to the target as the things it hits on the way in.

 

[holdencm9]

Basically it only matters if you think "energy dump" is a thing.

The energy that goes into the target is proportional to the squares of v1 and v2, where v1 is the velocity going in, and v2 is the velocity coming out.

So if the v2 is zero, all the energy was effectively "dumped" into the target. If the v2 is half v1, then 75% of the energy was "dumped."

If the bullet is going 1000 fps in, and comes out the backside going 250 fps, 93% of the energy was still expended inside the target. So I don't really think it is too crucial, although I'd be interested to know if anyone has chronographed an FMJ 9mm going through 16" or so of gelatin and seen how fast it came out the other side. My guess is it would slow down by at least 50% but I don't know. You could still really hurt someone if it went through, which is bad, but sometimes I wonder if people are over-estimating the overpenetration, thinking it goes into a body at 1200 fps and comes out at 1150 fps.

The other issue is people conflating hunting with defense. In hunting, it may be good to get 2 holes, because that is more coming out to track, and the deer won't be able to do anything about it anyway. In defense, 2 holes doesn't do you much good if you missed vitals, you want to stop the bad guy from taking a machete to your throat, you have to hit something vital. a bullet with 3/4" expanded diameter is a lot more likely to do that, and I imagine it would hurt a lot more too, so even if you do miss, you are more likely to get the "psychological stop." Again just a guess, you'd have to ask someone who has been shot by both, to know for sure.

From a purely defense standpoint and no worry about bystanders, you'd want full penetration AND full expansion. I just don't think you get that too often from service calibers. And also people are trying to find a good balance of risk and reward. Personally I would be more concerned about missing with a JHP than overpenetration with an FMJ, but still use JHP for the reasons above.

 

[Doc3402]

Let me touch on a couple points. A projectile will not stop until all energy is expended. It's simple physics. Having a projectile stop at 12 inches should reach a vital organ, but if that vital organ is at the 12 inch mark very little, if any, energy will be expended on it.

Secondly, entrance wounds very rarely bleed externally unless they are on the down side of the body. Experience shows me that that is not the way most people land and remain. If they are capable of any motor function at all they tend to roll off the area of injury, which is the entrance wound.

So, going with the wound side up person, now you have a person with one more hole in them than they had a birth, and they have either rolled off it or they have fallen that way. This makes the blood pool in the body cavities. Thanks to gravity the blood will remain there without a strong pump to push it out.

Pay attention now. This is what saves most people's lives.

The blood pressure outside the vessels and the blood pressure in the body cavities will equalize. The wound cavity pressure and the body's own blood pressure actually level out and stop further blood loss from the blood vascular system. If the pressure is high enough to feed the brain this person will probably live long enough to get to the OR. Once the cavity is opened by the surgeon it's anybody's guess.

Put the person wound side down and they will bleed more, but probably not enough to cause loss of consciousness right off the bat. The first person that tries to help them rolls them wound side up and we are right back to where we started.

People with both entrance and exit holes can't build up pressure in the wound or body cavities without outside assistance. No matter which way you roll them, they leak. One side drains and one side provides a vent for the drainage. Unconsciousness sets in faster and death is more likely. These people normally won't make it to the OR if the injury is in the chest or a major vessel unless there is prompt medical intervention.

The majority of people that are shot with handguns don't die. Of those that do die within the Golden Hour the majority of them are hit in a vital organ and have an exit wound. The only ones that die instantly are shot in the brain. All other fatal gunshot wounds will leave the person conscious for at least a short period of time. It's human physiology and there's no arguing with it.

How long that period of time is depends on how quickly the pump fails. There are two ways to make the pump fail in the time frame we are talking about. You can shut it down neurologically, or you can cause a hemodynamic compromise. Hemodynamic compromise is caused by destroying the pump or removing the blood.

So, in the greater scheme of things what does this mean? People that are not instantly unconscious can still bring the fight to you. The sooner they pass out, the better. It makes no difference to me if they are saved later. All I want is to end the fight as quickly as possible, and failing getting that Golden BB shot, rapid blood loss to the outside of the body is the best way to do it.

One other thing I haven't seen mentioned in the JHP/FMJ debate is reliability of handgun operation. If I can get 99% reliability with a JHP and 100% reliability with FMJ, why would I risk a visit from Mr Murphy when I least need it? This is the life of myself or my loved ones we're talking about.

 

[jmr40]

Am I wrong in my supposition that purely for wounding potential, a bullet that both expands and penetrates completely through the target is the best option?

I would agree that this is the best you can hope for. It is not always possible, but I'm in favor of as much penetration as possible, as long as you get a hole roughly 1/2" in diameter. I wouldn't want trade bullet expansion for penetration however.

 

[Doc3402]

Am I wrong in my supposition that purely for wounding potential, a bullet that both expands and penetrates completely through the target is the best option?

That would be the ideal situation, but it's fairly hard to get in concealed carry calibers... unless you can conceal a 6 inch .44 mag. <grin> Relying on both expansion and full body perforation isn't that realistic with what most people can conceal on their person.

 

[Stevie-Ray]

Hey Doc, great info.

 

[Doc3402]

Thanks, Stevie-Ray.

 

[Cosmoline]

Doc3402's comments ring true.

The "energy dump" school of thought was, as far as I have been able to determine, cooked up as a selling point for expanding HANDGUN rounds. In reality the fact that your .45 mushrooms and stops dead mid-torso isn't a good thing. Its killing power ends where it stops.

If that same round is fired from a long gun and penetrates through-and-through, its lethality is greatly increased.

The raw energy of the bullet does not do the killing in either case. The tissue injury does the damage which leads to death. I believe our bodies are able to absorb the ENERGY of a bullet impact pretty easily. The problem comes when that energy is focused on a small point and driven through tissue, damaging it and leading to blood loss, shock and death.

 

[481]

The "energy dump" school of thought was, as far as I have been able to determine, cooked up as a selling point for expanding HANDGUN rounds. In reality the fact that your .45 mushrooms and stops dead mid-torso isn't a good thing. Its killing power ends where it stops.

If that same round is fired from a long gun and penetrates through-and-through, its lethality is greatly increased.

The raw energy of the bullet does not do the killing in either case. The tissue injury does the damage which leads to death. I believe our bodies are able to absorb the ENERGY of a bullet impact pretty easily. The problem comes when that energy is focused on a small point and driven through tissue, damaging it and leading to blood loss, shock and death.

Cosmo,

Probably one of the best perspectives I've read in a long time.

Reminds me of this, taken from page 15 of "Bullet Penetration" by Duncan MacPherson, one of my favorite books on the topic-

The reason that kinetic energy and damage are not always correlated is that dynamic damage is not due to energy absorption, but to stress (force per area).

Having a lot of kinetic energy is nice, but it's what the bullet does with it that matters most.

Nice job.

 

[Vern Humphrey]

The "energy dump" school of thought was, as far as I have been able to determine, cooked up as a selling point for expanding HANDGUN rounds. In reality the fact that your .45 mushrooms and stops dead mid-torso isn't a good thing. Its killing power ends where it stops.

Or as I have said before, it isn't the raw energy, it's the hole that kills. The wider and deeper the hole, the quicker it kills -- assuming reasonable shot placement.

 

[Deus Machina]

Without digging through the whole argument so far...

I believe in the 'total track volume' thought, as described by hunters in the family.

Plenty of things survive a .3" hole clear through--at least long enough that you never find it--if you don't directly hit something full of nerves or blood.
A hole halfway through but with with a wound track that has been shredded promotes faster bleeding and can, with the right round, disrupt organs through hydrostatic shock.
A bullet that expands, disrupts matter, and just comes out the other side is perfect.

 

[hardheart]

Awesome information, this is great. Energy dump seems unlikely for wounding, with a major league fastball having more energy than a pistol round at the muzzle.

Without the velocity of rifle rounds, it would seem that handgun fired bullets are closer to bladed implements like arrows, spears, or knives in how they damage a target and stop it.

 

[T.R.]

Plain Jane 38 Special shooting 158 grain semi-wadcutter bullet has put a lot of bad guys 6 feet under. It hits a lot harder than paper charts would suggest. It shoots straight line penetration and does not bounce off bones.

TR

 

[coolluke01]

I've been thinking about this idea of energy dump. Many will say that a bullet that stays in the target dumps all it's energy there and is therefor more effective.
This link below talks about how much energy a punch has. The short story is that a punch delivers about 115 ft lbs of force.

A 9mm delivers about 320 and about 450 for +P+. A rushing attacker is not going to be stopped dead in their tracks with a punch. Double to triple that force? I still don't think it's going to make a huge difference. It's just too little too late.

Hitting vitals is far more important.


http://www.google.com/url?sa=t&rct=...0npB9i120taB_mNHw&sig2=LBokL0PxTdIenJUEfTcrLA

 

[Doc3402]

Plain Jane 38 Special shooting 158 grain semi-wadcutter bullet has put a lot of bad guys 6 feet under. It hits a lot harder than paper charts would suggest. It shoots straight line penetration and does not bounce off bones.

TR

What you say is very true, but there is another side to it. The .22 LR also kills a lot of people as does the .44 magnum. In the .44 it often seems like close is good enough. With the .38 there is a level of skill involved, and with the .22 you need to be very lucky on top of skillful.

One of my stock answers when asked what my preference of calibers would be if I had to get shot with something is the .38 Special out of a 2" barrel. The reason being

It shoots straight line penetration and does not bounce off bones.

... and it rarely makes an exit wound. The shooter would have to be very skillful or very lucky to get an immediately killing shot with one. Sure, it can happen, but I'm playing the odds. With trauma medicine the way it is today I would probably survive.

 

[Godsgunman]

I've always contemplated this question myself in trying to decide what carry ammo I want to use. Personally for me I have come to the conclusion that penetration is king and expansion is queen. (obviously this is only talking about the bullet itself, since we all know shot placement is king).
I mainly carry 9mm and in my own tests I have found that I do not trust a certain "popular brand" JHP because its expansion leads to too little penetration. So I've chosen one that while it may not expand as well, it does expand enough and give more penetration. Lets face it, if you are hitting where you should, the bullet will have to punch through the ribcage and/or sternum plus at least 10" IMO to be effective. Your shot will not always be AP or front to back it may be a side shot which would need more penetration to hit the important stuff.