Terminal Ballistics

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iMagUdspEllr

New member
A discussion on the handgun board inspired me to ask a question about rifle terminal ballistics.

There has always been many debates about .45 ACP vs 9mm. But, I want to talk about how rifle bullets stack up against each other as far as terminal ballistics are concerned.

When people select rifle bullets for long range shooting they are racked and stacked by their ability to get to the target and buck the wind (ballistic coefficients, higher muzzle velocities, etc.).

But, when a bullet gets there what makes one rifle bullet superior to another? Since the desired properties of a bullet change depending upon what the target is (e.g. What is good for coyote is not good for bear)... Let's stick to human targets.

Are all rifle bullets of the same design (FMJ, soft point, open-tip, etc.) the same near the end of their range?
I know a .50 BMG will sever limbs (obviously does wonders for causing someone to bleed out as fast as possible) but are there other types of damage going on? Handgun people talk about hydrostatic shock... well when does that start to happen? What causes that to occur?
 
I'm guessing you want to focus on military bullets....

All boat tail spitzer bullets will destabilize in tissue and "flip" to go base forward.

As far as caliber, smaller calibers will flip sooner than larger calibers.

Hydrostatic shock is not an issue with either pistol or rifle bullets until you get so much energy that the tissues can't bounce back from the shockwave. When that happens you get the "red mist" effect as the body of the animal couldn't contain the shock and it essentially exploded. Once you get into normal size animals, including humans, that doesn't happen, even with a 50 BMG.

If there is enough energy remaining on impact, the bullet will fragment during the flip, but this is largely velocity dependent and bullet construction dependent. If this critical velocity is not reached, even thin walled match bullets fired by snipers will have the same wound channel characteristics as FMJ.

That is the quick and dirty explanation. Google "Dr. Martin Fackler" and read everything he wrote, because he literally wrote the book on terminal ballistics.

Jimro
 
Nope, no need to stick with military bullets.

As far as bullets that flip... well when a M193 55gr 5.56x45 round flips and it has a high muzzle velocity (out of a 20" barrel for example) it has a tendency to fragment (turning one bullet into many) which seems to make it dealier than other "flipping" bullets. The Mk 262 77 gr Sierra OTM bullet was supposedly better than M193 out of shorter barrels. This was said to be due to the longer length of the bullet. The longer bullet would split in half even though the muzzle velocity wasn't high enough to cause the fragmentation demonstrated by the M193 out of longer barrels. That round seems to also be better than regular "flipping" bullets because the one bullet turns into two. This all happens after impacting the target, of course.

But, I have a hard time believing that a 5.56 is superior to larger calibers as far as terminal ballistics is concerned. If hydrostatic shock isn't caused by even a .50 BMG then the only advantages larger calibers seem to have is a longer range and barrier penetration capability. Is that right?
 
As far as bullets that flip... well when a M193 55gr 5.56x45 round flips and it has a high muzzle velocity (out of a 20" barrel for example) it has a tendency to fragment (turning one bullet into many) which seems to make it dealier than other "flipping" bullets. The Mk 262 77 gr Sierra OTM bullet was supposedly better than M193 out of shorter barrels. This was said to be due to the longer length of the bullet. The longer bullet would split in half even though the muzzle velocity wasn't high enough to cause the fragmentation demonstrated by the M193 out of longer barrels. That round seems to also be better than regular "flipping" bullets because the one bullet turns into two. This all happens after impacting the target, of course.

But, I have a hard time believing that a 5.56 is superior to larger calibers as far as terminal ballistics is concerned. If hydrostatic shock isn't caused by even a .50 BMG then the only advantages larger calibers seem to have is a longer range and barrier penetration capability. Is that right?
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You should look up Dr. Fackler's research on 5.56 fragmentation, it will list the velocities needed that you are looking for.

Suffice to say, a 5.56 bullet that fragments in flesh is "superior" to a 308 round that doesn't, both wounds can either be lethal or non-lethal depending on where they hit and what tissues are disrupted.

Yes a 50 BMG can rip a limb off as the tissues surrounding the limb are not enough to contain the hydrostatic shock, so you see the "red mist" effect like when shooting a prairie poodle with a 22-250. I have watched videos of a 50 cal cutting a guy in half, but he was scaling a cliff when he was shot and wasn't exactly a big guy to start with, so hydrostatic shock may have played a part, although I think it is more likely that it was in combination with ricochets of rock from the cliff face that cut enough tissue to allow the legs and torso to separate.

When you increase a bullet length, such as going from 55gr FMJ to 77gr OTM bullets, you have to increase twist rate to stabilize the bullet right? That is why the M16 started out with a 1:14 twist before moving to the 1:12 twist of the A1 to account for arctic conditions. With the 1:7 twist of the A2 and newer we got to use longer bullets. Bullets that need more twist to stabilize are also easier to destabilize on contact with flesh. The thin jacket of the 77gr OTM bullet will allow it to fragment at lower velocities than the 55gr FMJ, but there is a velocity floor there too.

But the Mk262 did allow the JSOC Jedis to get good lethality out of SBR rifles at CQB distances because the velocity floor was still a few hundred meters beyond CQB ranges. With M193 or M855 once you drop below 2,600 fps you are in the "non-fragmenting" zone, whereas the thinner jacket of the OTM bullet is more forgiving. If you could use a soft nosed spitzer bullet (aka a dum dum) then it wouldn't matter as much.

But believe what you want, there are lot of folks to will never be convinced that the 5.56x45 could ever be as good as the mighty 7.62x51 despite its excellent performance for the last 50 some years of military service.

Jimro
 
Are there fragmenting .308 rounds? I have only heard of this with .223.

What would a soft nosed spitzer bullet do? It would fragment regardless? Or are you saying it would expand and the expansion would cause similar damage to a fragmenting bullet of the same caliber?

I will google for Fackler's information about 5.56.

Hey, I'll believe it if that is true. More bullets, less recoil, and the same amount of lethality sounds fine by me. I guess I kinda want a "tier list" of rifle bullets. .50 BMG is on a completely different tier than 5.56 but where do all the bullets in between lie? Does Dr. Fackler's work have the information I need about that?
 
German DAG lots of 7.62x51 have been known to fragment, as has M118LR at close range.

A soft nose spitzer bullet will deform, or "mushroom" in tissue. This increases the size of the permanent wound cavity especially at lower velocities than required for fragmentation. That American M80 7.62x41 with a 147gr FMJ that doesn't fragment is going to have a smaller permanent wound profile than a 150gr boat tail spitzer bullet at the same velocity.

I've seen the 7.62x39 pushing Rem Corlokt bullets after the bullet was recovered from a deer. Perfect "mushroom" performance from the bullet despite only having 2,400 fps velocity at the muzzle.

Suffice to say that military bullets are designed to not deform, and hunting bullets (for varmints or big game) are designed to deform. But all bullets are lethal, and it is good to remember that.

Jimro
 
What would a soft nosed spitzer bullet do?
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SGK's, Berger VLD's (and others of similar construction) will fragement at high (2900+ f/sec) velocities, usually 2-3 inches inside a live target .....

..... and hydrostatic shock is a factor with high velocity expanding bullets. I have seen enough internal organs -hearts, lungs, livers, large arteries/veins- not in the path of bullets, but severely damaged nonetheless, to know it was not the bullet that did it, but the shock wave ..... turns out that some organs, like the liver, are not very elastic at all.
 
@Buzzcook: I know humans are easy to kill compared to many other animals. But, I was inspired to make this thread because of a handgun thread that was focused on self-defense (against people).

@All: So when does hydrostatic shock start to happen? What impact velocity/bullet grain/bullet construction triggers this effect to occur? I see a few examples were given for bullets that will fragment or mushroom. Which leads me to ask what is best for terminal performance?

A) Fragmentation
B) Expansion
C) Hydrostatic shock
D) All of the above

Do we have to pick and choose? Can we have fragmentation and hydrostatic shock? What would you choose and why?

From what I'm reading, as long as the bullet fragments or causes hydrostatic shock it will be deadlier than bullets that don't.
 
iMagUdspEllr,

From what I'm reading, as long as the bullet fragments or causes hydrostatic shock it will be deadlier than bullets that don't.
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Basic anatomy for terminal ballistics.

Central nervous system is the brain, brain stem, and upper spinal column. If you destroy any of those, you have achieved "dead" or "immediately stopped the threat."

Outside of the CNS, you have two things that generally keep an organism alive, the respiratory and circulatory systems. That is the stuff that handles the "air going in and out and blood going round and round."

To kill an organism with a bullet (excluding CNS shots) you need to disrupt that cycle of "air going in and out, blood going round and round." This is why ethical hunters go for the traditional "heart/lungs shot" from a broadside if they can get it, although an angling shot will work too.

What really causes death is when the circulatory system can no longer supply the CNS with enough oxygen to continue function, which means the lungs have either been filled up with blood, and the animal drowns, or the blood is not being circulated because the heart is destroyed, or "exsanguination" occurs to the point where there simply isn't enough blood to support life.

In any of that, did I talk about which bullets were "deadlier"? No, I did not. An FMJ will kill things every bit as dead as a Nosler Partition or Sierra Match King.

Now, if you are talking about which bullets will kill an organism the fastest, the answer to that is the one that is placed into the lethal zone with best accuracy. Hydrostatic shock does a similar thing in human tissue that a "blast wave" does, and the most susceptible tissue to that is the brain.

Shoot someone in the liver and they will likely die without medical care. Shoot someone in the leg where it goes through and through and they won't even get medevac'd off the FOB. Watched a CPT walk around with a limp for days after an AK round went through and through the his thigh. That same shooter killed one of our E4 mechanics with the same rifle firing the same ammunition.

The biggest indicator of bullet performance to lethality is "permanent wound cavity" as it is the permanent hole that lets the blood out. This is a really poor way to measure lethality but it is better than nothing. If all else is equal, the bullet that produces the bigger permanent wound cavity will be "deadlier" to use your words. But ALL BULLETS ARE LETHAL, and alive and dead are binary states, you are either dead, or you aren't.

Jimro
 
@Jimro: Understood. But, I guess I'm using the word incorrectly. But, I consider an RPG deadlier than a .22lr. They might both kill you but one is harder to be hit by and still survive.

Thank you for all the information.
 
Since RPG's are lumped in with "Small Arms Fire" as a cause of death I have no way of differentiating how deadly RPGs are verses traditional rifle fire, but suffice to say an RPG will qualify as a "weapon of mass destruction" for legal purposes in the US for a reason.

Jimro
 
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