Wound Ballistics

[Quartus]

I wasn't trying to turn this into a 5.56mm vs 7.62mm debate.

Me nuther! Just pointing out that there are tradeoffs. The decision is not clear cut. BTW, have you tried shooting several hundred rounds of 7.62 in a short space of time? Might change your mind about handling recoil. But then again, what YOU can do or JOE SHOOTER can do isn't really the issue when you are deciding on a combat rifle for infantry types. It's about what Joe AVERAGE can do. And, like carrying ammo, EVERYONE can take less recoil better than they can take MORE recoil.


BTW, folks, the 5.56 was not DESIGNED to tumble. It does sometimes, and sometimes not, but it wasn't DESIGNED to do so.

So tell me, Oh Dissenters, why is the 5.56 the only round that is "designed to tumble" when it has the same characteristics as many other rifle rounds that were NOT designed to tumble? And what is it about its design that makes it tumble?

 

[cordex]

why is the 5.56 the only round that is "designed to tumble" when it has the same characteristics as many other rifle rounds that were NOT designed to tumble? And what is it about its design that makes it tumble?

5,56mm isn't the only bullet that tumbles.

Rear-weighted bullets of all kinds of calibers happily become unstable and reverse themselves putting the heaviest part forward. Good ol' Spitzer.

Now, it just so happens that because of the design of the military 5,56mm bullets, they tend to tumble at a reasonably early point in the wound, and have a thin enough jacket that they can reliably break up when fired into tissue at a high enough velocity.

Or so I grok.

 

[Quartus]

EggsTACKLY! There are plenty of rounds that will tumble, but you don't hear about them being "designed to tumble". Somehow that only applies to the Evil Leg Blowing Off 5.56 mm.


The Urban Legend That Wouldn't Die!

 

[444]

"Unlike most FMJ rounds, M193 and M855's primary wounding mechanism is fragmentation. This is a good thing because without fragmentation these rounds otherwise would act like a ice pick and cause very little damage because of their small size. At the proper velocity, both M855 and M193 strike flesh and immediately begin to yaw (tumble). Contrary to rumor and popular media belief, this is not unique to these rounds. All FMJ bullets with tapered noses will tumble in flesh with enough velocity, because their center of gravity is aft of their length center--causing them to want to travel "tail first" in denser mediums (like water and tissue).

If the rounds are moving fast enough when they yaw to about 90 degrees of their original trajectory the stress on the bullet from traveling sideways through a dense medium (tissue) will overcome the structural integrity of the bullet and it will start to break up.

If the velocity is high enough this breaking up is pretty dramatic and causes equally dramatic wounds. This is because the fragments travel rapidly through the temporarily crushed tissue and tear it. Most tissue is very elastic and will stretch quite far before returning to its normal shape (this is called the temporary crush cavity) but the addition of quickly moving fragments makes permanent the cavity that might otherwise have returned after the impact and therefore creates a much larger wound."

http://www.ammo-oracle.com/

 

[Shawn Dodson]

...this is called the temporary crush cavity...

I've been meaning to get ahold of Troy and have him correct this error.

It should read: ...this is called the temporary cavity....

 

[Newton]

So, now being intellectually armed with all this 5.56mm uberammo information about tumbling, fragmentation, cavitation, sonic pressure waves, and 15cm exit wounds, I am left with just one question.

How come the grunts are having to shoot people 6 times to stop them, and are picking up the ballistically inferior 7.62x39mm weapons when they get a chance (I know the reasons for this aren't that simple - but it is happening - AGAIN).

7.62x39mm isn't supposed to kill people very effectively, it seems the only thing it can't do in reality, is read technical reports on it's lack of effectiveness. 5.56mm performs wonderfully on Al Quaeda gelatin blocks wearing denim head scarves, but in the real world it just "icepicks" people.

I am SO confused by this gulf between theoretical and actual performance, can anyone answer THAT question, I just don't see inadequate barrel length being the only reason (that poor orphan the M4) ?

 

[cordex]

How come the grunts are having to shoot people 6 times to stop them...?

Because real people don't fly back sixteen feet through a plate glass window every time they're shot with a real gun.
Because small arms in general aren't great shakes at "manstopping" - doesn't matter if you're usting .308 short or .223 or .300 SUPERDUPERUBERMAGNUM ... shot placement is the key.
Because in real life, people can be hurt extremely badly - even mortally - and keep fighting.
Because six shots is two pulls of the trigger when set to burst, and can be fired in less than a second on auto and that's hardly enough time for someone to even realize they're shot, much less stop fighting.

5,56mm does it's job well enough for me. And the vast majority of real US combat troops (as opposed to x-ray techs and supply crews) are pretty happy with it too.

 

[brownie0486]

It's not a battle rifle. They [ BR'S ] don't have the problem of put down.

Lots of m-14's brought out of mothballs for the latest fights in Iraq and Affieland.

.223 is for varmits under critters up to about 70 pounds reliably. After that it's iffy. When the poo is flying, iffy doesn't get it.

We [ the US military ] are learning all over the benefits of the BR and it's no nonsense killing power on humans, that is why we are they isn't it.

The 223 has a place somewhere but it is not on the battle fields of the world. For that you need a battle rifle.

Brownie

 

[Quartus]

5.56mm performs wonderfully on Al Quaeda gelatin blocks wearing denim head scarves, but in the real world it just "icepicks" people

Well, if that were true, the explantion would be that the current ammo/rifle has enough lower velocity to make a big difference in the wound it creates. (It is a big difference.)



Any and all proponents of the "icepick" theory are welcome to come to the range with me for a demonstration. (Assuming the range is in some third world hole with bribable authorities and no extradition treaties with the US.) We'll blindfold you, shoot you once with the current mil spec ammo and rifle, once with the VietNam era versions, and once with a "real man's BATTLE RIFLE" and you can tell us which was which.

 

[Shawn Dodson]

...in the real world it just "icepicks" people.

Two reasons:

1. The 62gr M855 cartridge is being fired from an M4 carbine, which has a 14.5" barrel. The M855 was designed for the M249 SAW, which has a barrel length of ~20", similar to the M16A2 rifle. The shorter barrel length of the M4 carbine robs the bullet of velocity needed to fragment when it yaws.
2. M855 bullets exhibit variations in terminal performance. Some bullets yaw and fragment while others yaw.
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[MeekandMild]

Remembering the training I had at the infamous Fort Sam Houston goat-shoot, and from my deer hunting experiance, when you want to remove damaged muscle, et cetera from around a supersonic bullet wound you have to cut out a hole roughly 30 times the diameter of the bullet.

OTOH, from my experiance looking at holes made by the "Saturday Night Metropolitan Knife and Gun Club" subsonic wounds are more of the "ice pick" variety. Fat ice picks, but ice picks nevertheless, especially the .25, .32 and .380 wounds.

Many variables here.

Like the aerospace engineers say, in theory there is no difference between theory and practice but in practice there is.

 

[Newton]

Any and all proponents of the "icepick" theory are welcome to come to the range with me for a demonstration. (Assuming the range is in some third world hole with bribable authorities and no extradition treaties with the US.) We'll blindfold you, shoot you once with the current mil spec ammo and rifle, once with the VietNam era versions, and once with a "real man's BATTLE RIFLE" and you can tell us which was which.

An ironically accurate description of current conflicts, except the blindfolds are typically worn 4 inches higher.