5.56 "tumbles" in people says OLN...

[WillBrink]

I was watching OLN Wed line up of gun shows, and one had a dedication to the AR, with some interesting historical info on the AR. I forget which program it was, perhaps Shooting USA. Then they get to someone who starts discussing the 5.56. He says that many didn't trust the little bullet, but it turned out to be more effective then the bullet it replaced.

That gets my attention. Then he says, the 5.56 is so effective because it "tumbles" in the target (no, he didn't say yaws and fragments but "tumbles") and the larger bullet it replaced (he never said 7.62 BTW) just made holes in people.

Wow, kinda thought knowledge base out there was better then that, and or, perhaps someone with actual knowledge of the topic screened the show for accuracy.

Anyone see that show? Might have been Shooting USA. I enjoyed the historical look at the AR (didn't learn anything, but it was nice to see the black rifles getting such credits) but had hoped that type of poor info was long gone.

[Carnut]

That information has been going around for a very long time. My brother who served in southeast Asia in the late '60s heard that from the sergeants who trained him.

[polymorpheous]

Wasn't there something about the original twist rate that barely stabilized the 55gr. projectile?
Was it 1:14? Then the Air Force needed it changed to 1:12? Or vice versa?

This is the story I heard anyways.
I don't know if it is true or not.

[wahoo95]

Could it be that you are being a little overly critical of what he said? I guess it depends on how you look at things.....

To me the thought of a bullet tumbling is more of a "laymens term" for yawing and fragmenting making it easier for those with little or no knowledge on the subject to understand. You also have to keep in mind that the fragmentation was the best case, however not always a given. If the bullet yaws and doesn't fragment wouldn't that simply mean it tumbled?


The orginal twist was 1/14 which made the bullets more likely to tumble or yaw.

[WillBrink]

Could it be that you are being a little overly critical of what he said?

On the "tumbling" aspect perhaps, but the the 5.56 being more effective then the bullet it replaced, no. Have heard the tumble thing many times as you all have, and as you said, perhaps an overly simple easy way to explaining terminal ballistics.

But, more effective then the bullet it replaced? No way to spin that one, it's just faulty info.

Never heard that particular bit of info before as it relates to 5.56.

[wahoo95]

On the "tumbling" aspect perhaps, but the the 5.56 being more effective then the bullet it replaced, no. Have heard the tumble thing many times as you all have, and as you said, perhaps an overly simple easy way to explaining terminal ballistics.

But, more effective then the bullet it replaced? No way to spin that one, it's just faulty info.

Never heard that particular bit of info before as it relates to 5.56.

I guess it again depends on how you look at it. Everyone knows that 7.62 is very effective, however on human targets it really excels when there is cover involved. The larger heavier mil ball round will expend most of energy well after passing through a person, unlike 5.56 which will expend all of it energy into the target. Its tough for a bullet to be good at both. I guess it really depends on how you look at it.

[Doc Safari]

Wasn't there something about the original twist rate that barely stabilized the 55gr. projectile?
Was it 1:14? Then the Air Force needed it changed to 1:12? Or vice versa?

This is the story I heard anyways.
I don't know if it is true or not.

The version I heard:


The original M16 barrel had a 1:14 twist. This barely stabilized the bullet, which tended to tumble on impact. Early troops were very happy with this, because it caused very catastrophic wounds. If it hit you in the arm, it would take your arm off. If it hit you in the gut, it would disembowel you. Troops nicknamed the gun the "meat axe."

So in steps the military, who didn't like how that rifling twist would not stabilize tracer rounds sufficiently to meet accuracy requirements. The rifling was changed to 1:12 and the rifle and cartridge no longer had the devastating effect on targets.

[WillBrink]

I guess it again depends on how you look at it. Everyone knows that 7.62 is very effective, however on human targets it really excels when there is cover involved. The larger heavier mil ball round will expend most of energy well after passing through a person, unlike 5.56 which will expend all of it energy into the target. Its tough for a bullet to be good at both. I guess it really depends on how you look at it.

I'd say we need an expert such as Dr Roberts to comment on the above, but my understanding is the 7.62 has superior terminal performance across the spectrum regardless of how you choose to look at it, all things being equal*

*= That is comparing apples to apples of the version of the rnd.

[polymorpheous]

The version I heard:


The original M16 barrel had a 1:14 twist. This barely stabilized the bullet, which tended to tumble on impact. Early troops were very happy with this, because it caused very catastrophic wounds. If it hit you in the arm, it would take your arm off. If it hit you in the gut, it would disembowel you. Troops nicknamed the gun the "meat axe."

So in steps the military, who didn't like how that rifling twist would not stabilize tracer rounds sufficiently to meet accuracy requirements. The rifling was changed to 1:12 and the rifle and cartridge no longer had the devastating effect on targets.

This is almost verbatim what I've read.
I didn't take too much stock in it.

[Heavy Metal]

The version I heard:


The original M16 barrel had a 1:14 twist. This barely stabilized the bullet, which tended to tumble on impact. Early troops were very happy with this, because it caused very catastrophic wounds. If it hit you in the arm, it would take your arm off. If it hit you in the gut, it would disembowel you. Troops nicknamed the gun the "meat axe."

So in steps the military, who didn't like how that rifling twist would not stabilize tracer rounds sufficiently to meet accuracy requirements. The rifling was changed to 1:12 and the rifle and cartridge no longer had the devastating effect on targets.

That's what I heard too. Of course it has since been totally debunked.