Alphazulu6
member
5.56 tumbles. I have seen it first hand when the wound channel hits solid tissue. Otherwise I have seen it go completely through an individual and really did not cause much damage other than a neat little hole.
5.56 tumbling on impact
- Thread starter Rokman
- Start date
- Status
Vern - you got me. The Black Rifle goes into exhaustive detail on the process, but I don't know that there was any "document." Stoner was working on his own and what he was thinking nobody will know. The cartridge itself was worked on by Stoner with Bob Hutton, IIRC.
LaEscopeta
Member
If I remember correctly from what I’ve read, the Army adopted (was forced to adopt) the M-16 and the 5.56mm ammo based on the ROC from the previous rifle development competition, the one that chose the M-14 over the AR-10 and the FAL (also some other rifles?) That previous ROC required the round to penetrate both sides of a standard army helmet at some distance (600 yards? 400?) Stoner, Horner et al designed the new AR15 and the 55 grain 5.56mm bullet to pass that test and most (all?) of the other tests from the previous army ROC.
When the defense department civilians (McNamara among them) heard this they figured the new M-16 would do everything the army said they wanted, plus be controllable on full auto. The M-14 was not controllable on full auto, and army doctrine stated full auto was required for most infantry. So if the army got the M-16/5.56mm forced on them, it was sort of a case of being careful saying what you want because you might get it.
As stated above, tumbling was not a requirement of any of the army ROCs, and the M-16/5.56mm was not designed to tumble in tissue. Although by coincidence it often does
SDC
Member
According to both "The Black Rifle" and "The History & Development of the M-16 Rifle and its cartridge", when they first started producing the M-16, it was rifled with a 1:14 twist, the same as for commercial .22 centrefire bolt-action sporters of that period (which invariably used short, lightweight bullets around 40 grains); by 1963, when the Army got serious enough about the rifle to start doing some serious testing, they had noticed that that 1:14 twist and the 55-grain bullet was marginal for accuracy at best, especially in cold, dense air (and what are you going to do if you NEED that rifle in January in Germany? Call a truce until July?) So, the rifling twist was changed to 1:12. After further study, and a decision that better penetration/mild AP ability was needed, they standardized on the SS109 projectile, which became the M855 ball, and which necessitated a faster twist rate of 1:7, where it is today.
After soft point bullets were outlawed under the Hague convention the Brits loaded the .303 FMJs with aluminum at the tip and lead through the body and base. That was intended to increase the tumbling effect of the bullet travelling through tissue.
Vern said:
I have no proof, but I would say the bullet tumbling was ad copy from Colt or Dick Butell who was the brains behind Fairchild when they were designing the AR15 and ctg. He tried to sell the gun to all sorts of buyers showing its lethality on watermelons, etc. but no takers due to the recent adoption of 7.62mm by NATO. After languishing a few years, Fairchild was happy to sell the rights to the AR15 lock, stock, and bbl to Colt, who further developed the gun and marketed it for several years before they got the original order from the Air Force. Then Macnamara, etc.
I have no proof, but I would say the bullet tumbling was ad copy from Colt or Dick Butell who was the brains behind Fairchild when they were designing the AR15 and ctg. He tried to sell the gun to all sorts of buyers showing its lethality on watermelons, etc. but no takers due to the recent adoption of 7.62mm by NATO. After languishing a few years, Fairchild was happy to sell the rights to the AR15 lock, stock, and bbl to Colt, who further developed the gun and marketed it for several years before they got the original order from the Air Force. Then Macnamara, etc.
Vern Humphrey
Member
That would, then be post-design.
In fact, I have seen the same thing in print about the M14, before the AR15 was on the horizon. During the Civil War, both sides (using identical moulds to produce their bullets) accused the other of using bullets designed to push cloth into the wound. In the Revolutionary War, a British officer charged rifle bullets "twist their way through flesh."
Someone's always claiming there's something eeeeevil about the way normal ammunition works.
Bullets from the 5.56 X 45 don't behave any differently from any other FMJ bullet, other than some of them having a tendency to fracture along the cannelure -- but the fracturing effect was not claimed in the ad copy.
Heh heh - it's true that everybody claims the other side is taking unfair advantage of whatever.
If you will remember, Fairchild originally developed the AR10 - a 7.62 version of basically what we know as the AR15. Unfortunately, the AR10 had a titanium bbl inside an aluminum sleeve, IIRC. This blew up in one or two situations - looked like Elmer Fudd's shotgun bbl when Bugs stuck his finger in the end - in other words, it looked like a banana peel.
Several possible buyers backed out and they sold a few to the East Indies or somewhere, but the FAL was the weapon of choice, adopted by most all western countries.
The AR15 was reverse engineered from the AR10 by somebody other than Stoner, as I recall. Stoner had by that time moved on to Cadillac Gage and the Stoner 63 program, IIRC.
If you will remember, Fairchild originally developed the AR10 - a 7.62 version of basically what we know as the AR15. Unfortunately, the AR10 had a titanium bbl inside an aluminum sleeve, IIRC. This blew up in one or two situations - looked like Elmer Fudd's shotgun bbl when Bugs stuck his finger in the end - in other words, it looked like a banana peel.
Several possible buyers backed out and they sold a few to the East Indies or somewhere, but the FAL was the weapon of choice, adopted by most all western countries.
The AR15 was reverse engineered from the AR10 by somebody other than Stoner, as I recall. Stoner had by that time moved on to Cadillac Gage and the Stoner 63 program, IIRC.
DMK
Member
Excellent post!def4pos8 said:
RobTzu
Member
Air is a fluid. It is not a liquid. But liquids are fluids too.
ranger335v
Member
- Joined
- Dec 3, 2006
- Messages
- 3,797
Many myths of tumbling 5.56mm GI ammo rises from a misunderstanding of how and why the wounds are often massively out of proportion to what might normally be anticipated from larger, heaver, slower moving bullets. Any enlongated bullet that doesn't disintergrate and if the penetration is sufficent, will veer off path, swap ends and tumble, not just the 5.56. Such veering and sometimes tumbling was a bugaboo of elephant guns firing slow, heavy solids a hundred years ago!
All bullets want to tumble in flesh. Any light weight projectile is inherently less stable after impact than a heavy one of the same shape. A .22/55 gr. bullet will loose stability much more rapidly than a .30/150-170 gr. bullet but neither can tumble many times before penetration stops.
We all know that spin only provides sufficent stability for bullets to stay point on IN AIR. In the massively higher density of flesh, the spin would have to be impossibly fast to keep light bullets stable. But even those bullets that tumble a time or two in a torso can't instaneously start to spin end-over-end like a buzz saw, as some folks seem to believe!
The unexpectedly high "tumble" rate of the 5.56 occurs when the very solid and fast, light bullet suddenly enters a more dense medium that tends to make the point slow and veer off track while the heavier base is still trying to move straight ahead. As the bullet turns and then skids sideways, its larger side profile momentarily but vastly increases the energy tranfer to the unfortunate "target". (Note the wide variations in wound cavity when the bullet changes attitude as it tumbles through the ballistic gell in the excellant photo posted above.) But tumbling wasn't a deliberate design goal of the military, Stoner just used the twist rate for best accuracy with 50-55 gr. bullets in air. And that is far too slow to keep light bullets point-on in flesh.
Much 5.56 wound damage is due to the high velocity impact pulse, alone. A light bullet slows down a LOT when it impacts flesh, converting much more of its kinetic energy to heat and hydrostatic effect than a heavier but slower bullet that would carry through better could do. That "hydrostatic" damage WAS a hoped for result of the small bore, high velocity design!
The bullet enters stable and becomes unstable rapidly but time is required to tumble. A bullet traveling 3,000fps will fully pass through a six inch diameter arm or leg in only .00016 seconds IF it doesn't slow. Even slowing - a lot! - leaves very little time for it to tumble much, so it follows that the nasty damage to limbs is almost all due to the speed of impact. At those speeds, a little velocity improvement significantly increases the hydrostatic effect.
The ability to shatter a cinder block only requires a sufficently violent (hi speed) impact to a thin side-wall of that very brittle material. Even hard cast, relatively slow moving pistol bullets - and karate warriors - can shatter cinder blocks, no tumbling required. Instead of tumbling when stricking such a hard surface, most light bullets, even a lead core FMJ, will instantly rupture but great damage can be done by the impact itself. I've busted blocks with my .22-250 and 50 gr. varmit bullets and surely there was no tumbling there! A block wall can easily be shattered by the repeated impacts of a full-auto weapon.
All bullets want to tumble in flesh. Any light weight projectile is inherently less stable after impact than a heavy one of the same shape. A .22/55 gr. bullet will loose stability much more rapidly than a .30/150-170 gr. bullet but neither can tumble many times before penetration stops.
We all know that spin only provides sufficent stability for bullets to stay point on IN AIR. In the massively higher density of flesh, the spin would have to be impossibly fast to keep light bullets stable. But even those bullets that tumble a time or two in a torso can't instaneously start to spin end-over-end like a buzz saw, as some folks seem to believe!
The unexpectedly high "tumble" rate of the 5.56 occurs when the very solid and fast, light bullet suddenly enters a more dense medium that tends to make the point slow and veer off track while the heavier base is still trying to move straight ahead. As the bullet turns and then skids sideways, its larger side profile momentarily but vastly increases the energy tranfer to the unfortunate "target". (Note the wide variations in wound cavity when the bullet changes attitude as it tumbles through the ballistic gell in the excellant photo posted above.) But tumbling wasn't a deliberate design goal of the military, Stoner just used the twist rate for best accuracy with 50-55 gr. bullets in air. And that is far too slow to keep light bullets point-on in flesh.
Much 5.56 wound damage is due to the high velocity impact pulse, alone. A light bullet slows down a LOT when it impacts flesh, converting much more of its kinetic energy to heat and hydrostatic effect than a heavier but slower bullet that would carry through better could do. That "hydrostatic" damage WAS a hoped for result of the small bore, high velocity design!
The bullet enters stable and becomes unstable rapidly but time is required to tumble. A bullet traveling 3,000fps will fully pass through a six inch diameter arm or leg in only .00016 seconds IF it doesn't slow. Even slowing - a lot! - leaves very little time for it to tumble much, so it follows that the nasty damage to limbs is almost all due to the speed of impact. At those speeds, a little velocity improvement significantly increases the hydrostatic effect.
The ability to shatter a cinder block only requires a sufficently violent (hi speed) impact to a thin side-wall of that very brittle material. Even hard cast, relatively slow moving pistol bullets - and karate warriors - can shatter cinder blocks, no tumbling required. Instead of tumbling when stricking such a hard surface, most light bullets, even a lead core FMJ, will instantly rupture but great damage can be done by the impact itself. I've busted blocks with my .22-250 and 50 gr. varmit bullets and surely there was no tumbling there! A block wall can easily be shattered by the repeated impacts of a full-auto weapon.
Zak, the images you posted are from an article by Dr. Martin Fackler. The whole arrticle with images can be found here.
http://www.fen-net.de/norbert.arnoldi/army/wound.html
http://www.fen-net.de/norbert.arnoldi/army/wound.html
Tony Williams
Member
Yes, all FMJ spitzer bullets turn over to travel base-first when passing through a much denser medium than air (water, flesh, it makes little difference). The rate at which they tumble is mainly determined by their size and their construction.
Other things being equal, the smaller the bullet the faster it will tumble. This is partly why the 5.56mm has acquired such a reputation. Other things being equal, a 7.62mm will turn over more slowly, and a .50 cal hardly at all - but then, it doesn't need to
The constuction of the bullet matters if it affects the weight distribution. The British .303 Mk VII ball has already been mentioned: the light-alloy filled tip shifts the centre of gravity to the rear, so once it hits something it tumbles quickly. The Yugoslavian 7.62x39 AK bullets have a lead core rather than the steel one of the Russian original, and this shifts the CG to the rear which also means they tumble faster.
OTOH a parallel-sided round-nosed full-jacket bullet yaws hardly at all. That's why elephant gun ammo has round-nosed bullets - so they'll plough straight on through to the vitals. A pointed bullet would veer off in an unpredictable direction. The early round-nosed full-jacket military rifle rounds also tended just to drill a neat hole. The pointed spitzer FMJ bullet was invented for aerodynamic reasons but the tumbling effect was, you might say, a happy accident (unless you're on the receiving end).
Other things being equal, the smaller the bullet the faster it will tumble. This is partly why the 5.56mm has acquired such a reputation. Other things being equal, a 7.62mm will turn over more slowly, and a .50 cal hardly at all - but then, it doesn't need to
The constuction of the bullet matters if it affects the weight distribution. The British .303 Mk VII ball has already been mentioned: the light-alloy filled tip shifts the centre of gravity to the rear, so once it hits something it tumbles quickly. The Yugoslavian 7.62x39 AK bullets have a lead core rather than the steel one of the Russian original, and this shifts the CG to the rear which also means they tumble faster.
OTOH a parallel-sided round-nosed full-jacket bullet yaws hardly at all. That's why elephant gun ammo has round-nosed bullets - so they'll plough straight on through to the vitals. A pointed bullet would veer off in an unpredictable direction. The early round-nosed full-jacket military rifle rounds also tended just to drill a neat hole. The pointed spitzer FMJ bullet was invented for aerodynamic reasons but the tumbling effect was, you might say, a happy accident (unless you're on the receiving end).
RecoilRob
Member
http://www.gunboards.com/forums/topic.asp?TOPIC_ID=92115
A fairly comprehensive reporting of the development of the MKVII 303. Of course, the bullet does not 'buzz saw' through a target, but it most certainly will turn base first in short order after striking. And, more often than not, fragment.
And, anyone who believes that this phenomenon was an 'accident' is underestimating the ammunition developers. Moving the CG as far aft as possible is by design. They could just as easily put an aluminum base cone in to maintain the BC, but they chose to put it in the nose. Because that made it unstable when it hit.
A fairly comprehensive reporting of the development of the MKVII 303. Of course, the bullet does not 'buzz saw' through a target, but it most certainly will turn base first in short order after striking. And, more often than not, fragment.
And, anyone who believes that this phenomenon was an 'accident' is underestimating the ammunition developers. Moving the CG as far aft as possible is by design. They could just as easily put an aluminum base cone in to maintain the BC, but they chose to put it in the nose. Because that made it unstable when it hit.
Vern Humphrey
Member
Accuracy is enhanced by moving the center of gravity aft of the center of aerodynamic pressure.
RecoilRob
Member
I'd appreciate a dissertation on how moving the CG rearward increases accuracy. Any more info?
- Status
Similar threads
