Why does penetration matter?

I would think that higher penetration equals less time for expansion
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That makes no sense at all

Any expansion takes place in milliseconds, and the same applies to penetration

The higher the velocity, the more likely there will be expansion AND deep penetration, as long as the projectile doesn't come apart

You can't push a bellet so fast it won't "have time" to expand.

That's not how the physics works
 
Personally, I don't penetration much matters at all in most defensive situations. You are not deer hunting, and the objective is not a carefully placed shot for a quick clean kill. You are trying to stop and attack by incapacitating him or causing him to flee. A bullet through a lung will certainly kill a man, and has a high likelyhood of being fatal, but may not necessary incapitate or stop an attack as fast as the shock you tranfer if you hit bone and/or double the projectile size and add blades around the edges. O guy with a small pass through hole through his lung can often pull a trigger many times before he dies.
 
Why are people so obsessed with penetration of hollow points?
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Other than marksmanship, that's about my only concern. Expansion is nice; wound cavities, both temporary and permanent, are nice; but without marksmanship and penetration, the rest doesn't matter.
The concept of "overpenetration" puzzles me a bit, anyway.
 
tahunua001 said:
I do not agree with the 16 inches necessary BS that the FBI recommends. unless you're shooting up from the floor vertically through the entire torso or you're taking on a body builder, you would never in a million years need 16 inches of penetration, the human heart lies meer inches from the rib cage in any direction, 6 inches would be lethal, and have little chance of overpenetrating but what do I know? I'm just some guy from the internet.
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The reason the FBI protocol is for 12"-16" of penetration is because they are aiming for a worst-case scenario. It is actually not at all hard to come up with scenarios that are not even just possible, but likely, where you would need more than 6" of penetration.

First, a bullet may have to penetrate material in the way, such as heavy clothing. It may impact on more resistant body structures like bone. The person shot may be very large, whether muscle, fat, or both. And perhaps most commonly and importantly, a bullet that hits center mass may have to go through an arm on the way there, and it may be going through the long way on a transverse through the forearm.
 
So many folks get way too hung up on the FBI 12"-16" number. They forget that the FBI protocalls also call for going through car windshields, car doors, heavy clothing, and other barriers and still achieving those numbers.

As a non LEO, there are precious few times where firing through a car windshield would be a justified shooting.

In an article in another thread the author referenced a 158 gr. 357 fired through a carbine only penetrating 10 or so inches and failing this depth standard. Personally, I doubt a 158 gr. XTP fired at around 2000 fps. at 50 yards or less is going to fail to do the job simply because it failed to make the FBI last two inches.

Even from a handgun, a full energy dump into the agressor is still a full energy dump. Hitting the CNS, causing shock, hitting major arteries / veins, psycological stops, etc. are some of the things that "Stop" and attack.

22's have stopped attacks...but don't count on it. 45's have stopped attacks...but don't count on that either.
 
Interesting how 12-16'' penetration IN GEL is used, but you still rarely see LEO bullets having complete penetration, on COM hits, in many cases, even without barriers in the way...
 
Interesting how 12-16'' penetration IN GEL is used, but you still rarely see LEO bullets having complete penetration, on COM hits, in many cases, even without barriers in the way...
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That's true.
Most take it out of context and forget a little bone and clothing can equal several inches of gel
 
The use of gel is really only to provide a consistent test medium for comparing one bullet's performance to another. Think of it like a wind tunnel. Planes aren't designed to stay in a wind tunnel with consistent direction, temperature, density and humidity of air, but it lets engineers have a repeatable test for each design. From there, one can compare realworld performance and see that if a design works to a certain performance standard in that consistent medium, then the real world performance should be reasonably predictable, while it may not be identical to the performance in a controlled test medium.
 
There is no such thing as too much penetration. Complete pass throughs are desirable. If you get good expansion to go along with it then it is even better, but secondary.

The 3 keys to stopping a bad guy in order of importance...Placement, Penetration, Expansion.
 
I think the innocent little ole lady, or eight year old kid standing behind the bad guy or the mother of the baby in the stroller behind him would disagree.
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:rolleyes:

this again?

What about if you miss the BG and just straight up hit the innocent old lady?

Know what's beyond your target.

Also, a full pass through with an expanding bullet will deplete a majority of the projectile's energy. It's much less of a concern than a miss.
 
Based on my hunting knowledge which is pretty relevant here.....pass through is desired the large exit hole causes the loss of blood pressure that stops the aggressor. It addition, the temporary wound cavity is what determines the damaged zone for a hit. You need both. That is where JHP expansion matters. A JHP that expands rapidly, won't exit. A JHP that doesn't expand enough leaves with energy and a smaller temporary wound cavity.

So, in terms of importance to me:
1) pass through
2) diameter
3) controlled expansion
 
I don't look at it as either pass through or expansion, I tend to think of a good balance of both. I like the idea of a SD bullet to penetrate as it expands doing damage along the way. If I have to give up some of one to get the other I will give up some expansion for penetration.
 
Why penetration?

Consider the shooting of Lee Harvey Oswald. Although likely overstated, it was said by the coroner (I believe) that "...nearly every vital organ in his body was hit...". That is why penetration is important. Consider if he had been shot with a hollow point that expanded and therefore did not penetrate as it did. There would be a good possibility that he would have survived. So, you have to decide, do you want expansion to cause massive damage albeit at the cost of hitting deeper organs, or do you want to hit deep organs at the expense of expansion? You can have one or the other, not usually both.

In the case of a .45 Auto, where I doubt that it can get much expansion, I would likely choose a 230 grain hardball and go for penetration. On the other hand, in the case of a .357 magnum, I may opt for a lighter bullet choice to get maximum expansion because I have faith the ability to expand from its higher velocity. Or I could go with Jack Ruby's choice and shoot him with a .38 in the side where the organs were lined-up. Six of one, half a dozen of another.
 
Why are people so obsessed with penetration of hollow points?

"Power": To me the biggest attraction of a hollow point is the reduced chanced of over-penetration, i.e. shoot through. If your hollow points penetrate more and more wouldn't there be a higher chance of exiting your target and damaging whatever is behind it
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As folks have pointed out the point of jhp bullets is to create a larger permanent wound channel where more tissue is damaged. With jhps over the last 20 years the effort has been to create jhp bullets the both expand and penetrate 12-16" in 10% ballistic gel. Thus getting both expansion and adequate penetration to reach vital organs.

"Overpenetration" is not a concern, or should not be a concern, in the selection of a jhp bullet. You can't control "over-penetration" because you can't guarantee always hitting a part of the body where the bullet won't pass through. The only time it may be a factor in bullet selection is when you miss and live in an apartment building where the possibility of penetrating a wall can be lessened by selecting a hp bullet, if it expands.

So the idea that the best thing about jhp bullets is that they can prevent "over-penetration" is incorrect.

tipoc
 
I would like to seem documented cases of overpenetration. I haven't heard of too many cases of overpenetration with rifle ammunition, it seems to me that the argument over FMJ ammo vs. JFP/JSP is not that FMJ is bad but that JHP/JSP is so much better.
 
Cheapshooter: said:
Because there is no such thing as "knock down power". The only absolute sure way to cause an attacker to be instantly incapacitated is destruction of the central nervous system. Brain, and spinal cord. A large bleeding hole may stop an attacker, but it may take long enough for them to still do harm to their intended victim.
Just being shot could stop an attack. Destroying the central nervous system will stop an attack.
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That's a pretty concise perspective. Nice job. :)
 
I really do wonder about the goblin of "overpenetration". The eight year old grandma with a stroller and a baby in her arms getting shot by bullets that passed through the bad guy apparently doesn't make the news.

We hear, often about people wounded and killed by the police who MISSED the bad guy. Never about overpenetration injuries from police rounds (there must be some, right? but we don't hear about them, do we?), and the lack of any reports of innocents being wounded/killed, due to overpenetration, in civilian defensive shootings would make them seem even more rare. I've never heard of a verified one, although logic says there must be some.

As an institutional concern, for the beancounters, overpenetraion has a place, but I think it ought to be somewhere below officer marksmanship, and we all know what emphasis is placed on that....

And, just for consideration, what if its not Granny and the baby behind the bad guy, but three Nazi troopers lined up on the top of a tank? I think Indiana was happy with penetration that time. :rolleyes:
 
Those pesky arms have a bad habit of getting in the way:

armobstacles.jpg


During the 1986 FBI-Miami shootout five of nine participants (over 50%) were shot in the hand or arm.

A bullet that has to first perforate an arm before it hits and penetrates the torso can lose as much as 30% of it's total penetration potential. Thus a bullet that normally penetrates 10" may now penetrate only a total of 7". If this bullet must first pass through 4" of arm then there may be only 3" of potential remaining to penetrate the torso after it exits the arm.

The best performing bullets consistently penetrate between 14-16" of bare gelatin as well as gelatin covered by four layers of heavy denim cloth.
 
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