M16A1 tumbling bullet

Critics of the M-16 rifle say that the 5.56 X 45 bullet is too small to be really effective, unlike the 7.62 X 39 or 51 fired from the AK-47 and M14.

These reports did not surface as much during the Vietnam war due to the particular ballistics of the original bullet. Due to its specific ballistics, it tumbled when it hit soft flesh, causing huge wounds.

The current bullet does not have these characteristics.

What could be the benefit of a more stable bullet?

What could be the benefit of a more stable bullet?

Accuracy!

Roper

Too tired to fully research currently,but if i recall the bullet does tumble upon entering the body. The tip of the bullet is heavier/denser than the end. So when it hits the back end bends toward the front until it breaks apart. The military doesnt want rounds to go completely through the body. With the round breaking up inside the body cavity it causes more trauma,and killing the person quicker.


Found something here

The bullet’s pointed shape makes it heavier at its base than its nose, producing a center of gravity that is located aft of its longitudinal centerline. When the bullet hits the body and penetrates, the bullet attempts to rotate 180 degrees around its center of gravity to achieve a base forward orientation. This backwards orientation is the bullet’s stable position in tissue because it places the center of gravity forward.

At distances of 100 yards and under, when the bullet hits the body and yaws through 90 degrees, the stresses on the bullet cause the leading edge to flatten, extruding lead core out the open base, just before it breaks apart at the cannelure. The portion of the bullet forward of the cannelure, the nose, usually remains in one piece and retains about 60 percent of the bullet's original weight. The portion of the bullet aft of the cannelure, the base, violently disintegrates into multiple lead core and copper jacket fragments, which penetrate up to 3-inches radially outward from the wound track. The fragments perforate and weaken the surrounding tissues allowing the subsequent temporary cavity to forcibly stretch and rip open the multiple small wound tracks produced by the fragments. The resulting wound is similar to one produced by a commercial expanding bullet used for varmint hunting, however the maximum tissue damage produced by the military bullet is located at a greater penetration depth.

I was on the phone so I'll finish.

It is also the twist rate and bullet weight that made the bullet tumble.

AR's have 1-7, 1-8, 1-9, 1-10, 1-12 and I saw a barrel with a 1-14.

The 1-10 and 12 are better for light bullets.

My AR has a 1-8, so 69g to 77g are best for accuracy and longer ranges.

Roper

I heard from a Canadian officer that the 5.56 nato rounds were made not to tumble because tumbling bullets in wartime are forbidden by the Geneva Conventions.

The m16 round does tumble when it enters the body as well as fragmenting and causing immense damage.

In fact, the soviets decided that this was an advantage and created the AK-74. I am not sure if it fires the same exact round, but essentially it was meant to imitate the damage caused by the 223.

Now I've seen test in ballistic gel and the .223/5.56 does not tumble.

Tumbling could and does happen out the barrel if the length is wrong.
I know this because at a USPSA match my round started the key hole in the targets. Some how my Dillon seating die was off shorting the rounds.

Roper

As found on AR-15.com.


The original ammo for the M16 was M193, with a 55gr copper-jacketed lead-core bullet. The rifling twist on the first M16s was 1 turn in 14 inches, or 1:14. This twist rate was selected simply because it was the twist rate commonly used in the .222 Remington-chambered varmint rifles that the .223 round was based on. During tests of the M16 in arctic regions, it was found that the slow 1:14 twist wasn't fast enough to stabilize the 55gr bullet in the denser air. To correct this problem, the twist was tightened to 1:12 and all future M16s and M16A1s came with 1:12 barrels.

The M855 round and particularly the M856 tracer round, are very long bullets and require a faster twist rate in order to be stabilized in air. Firing M855 from a 1:12-twist rifle would result in an under stabilized bullet that would only fly straight for about 90 yards, then veer off as much as 30° in a random direction. In order to prevent soldiers from accidentally firing M855 in 1:12-twist rifles, M855/SS-109 was given a green-painted bullet tip. This allows M855/SS-109 to be differentiated from plain-tipped M193. M16A2s, A3s, A4s, M4s and M4A1s all have a 1:7 twist and can stabilize both M855 and M193.

I was under the impression that the bullet only tumbled after hitting something...so it actually tumbled in the AIR?

The original 55gr bullets fired from the slow twist rifling only tumbled on impact. No bullet tumbles in the air(at least not if you hope to be able to hit anything with it, as it'd have no accuracy).

The faster twist is to stabilize the heavier bullets, and to account for the arctic performance of the slower twist barrels.

Originally posted by Darce
I heard from a Canadian officer that the 5.56 nato rounds were made not to tumble because tumbling bullets in wartime are forbidden by the Geneva Conventions.

Never heard of any law or rule banning such bullets that tumbles in a person after impact.

Originally posted by deltaboy

Originally posted by Darce
I heard from a Canadian officer that the 5.56 nato rounds were made not to tumble because tumbling bullets in wartime are forbidden by the Geneva Conventions.

Never heard of any law or rule banning such bullets that tumbles in a person after impact.

Yes, because its BS. First, the often cited "Geneva Conventions" do not relate to the specific detail of legal or illegal weapons at all. The Geneva Conventions, put in a nutshell, regulate the treatment of the victims (on a broader scale) of war.

Second, the documents that weapons are subject to are the "Hague Conventions" and they only prevent the use of expanding bullets. The actual wording is:

The Contracting Parties agree to abstain from the use of bullets which expand or flatten easily in the human body, such as bullets with a hard envelope which does not entirely cover the core, or is pierced with incisions.

Source

So, tumbling isnt covered in there. It also doesnt say that only full metal jacket projectiles are allowed, another often-cited misconception. The FMJ is only the most common and de facto standard bullet to oblige to the Hague Conventions.

That doesnt say that every nation wasnt trying to maximize the wounding potential of their ammunition. The Soviet 5.45x39mm for example has a hollow tip beneath the jacket which sends the bullet to tumble when it hits a resisting surface. The US 5.56mm bullets have the tendency to fragment at high velocities (which, by the way, has been proven to be more effective a "showstopper" than simple tumbling). German DM16 7.62mm ammunition for example has a two-part core that enables fragmentation AND further penetration of the tip.

The current M16 round was redisigned to account for the Soviet Unions new body Armor. The new round would penetrate the armor and still break into 3 or more large peices, creating leathal damage.

These newer rounds are not working as well today on our Arab friends. With out the body Armor, the rounds go straight through, causeing very little damage.

www.special-operations-technology.com...

See paragraphs 3 and 4.

I've read better reports on this issue, but do not have the time at the moment to re-find them.

New user... recently purchased a Rock River Arms AR and have enjoyed getting to know the intimate details of its performance.

I just got caught up in this thread and began some casual web-research. In the process I found a site which seems to have some good info, and lots of interesting links relating to wound ballistics. It may be a bit of a bird-walk but some of you might find it interesting so I thought I'd share....

www.firearmstactical.com...

The 5.56x45 does tumble, and fragment, causing a large wound, but is seldom a wound that will drop a man in combat. THIS is the reason the round gets so much criticism.

The 7.62x39m43 used in the AK-47 is indeed a larger bullet, but it does not break apart or tumble. It is very good at penetration but leaves much to be desired in fatality.

The 7.63x51(.308) is an extremely effective round. It has enough power to punch through light armour, accuracy enough to serve in a designated marksman's rifle or sniper rifle, and light and practical enough for infantry. In my opinion, the 7.62NATO should be the primary round used by US troops.

The 7.62x54 Russian cartridge is a close match to its NATO counterpart, but dishes out a bit more accuracy and power. It is bulkier and harder to carry than the .308, but what do you expect from a 19th century cartridge. This is one of the oldest rounds still used, and it is encountered as frequently as the 7.62x39 is.

Originally posted by Nicotine1982
The 5.56x45 does tumble, and fragment, causing a large wound, but is seldom a wound that will drop a man in combat. THIS is the reason the round gets so much criticism.

AFAIK later testing suggests that it does not in fact tumble as used to be thought, but certainly does fragment - lots of details here -

matrix.dumpshock.com...

in Dr Fackler's classic study fo wound patterns produced by different rifle bullets.

"The large permanent cavity it produces, shown in the wound profile, was observed by surgeons who served in Vietnam, but the tissue disruption mechanism responsible was not clear until the importance of bullet fragmentation as a cause of tissue disruption was worked out and described. "

The original 5.56mm M193 round did have a tendancy to tumble more than the current issue 62gr varient. Thi was due to the lighter weight of this round.

All bullets tumble to some extent on impact with a surface. This is exacerbated by differences within the substance struck. With the human body, there are numerous structures encountered by a bullet on its' path through the victim, all with different masses (e.g. bone, muscle, organ tissue etc.). As the round moves between these structures, it bcomes unstable, causing a natural lateral rotation. This is the tumble described.

The heavier and faster a round is, the less prone it is to tumble, as it is generally more stable.

The tumble is not nearly as important in wound creation as the cavitation effect caused by the massive changes in pressure as the round enters and exits the body, or the fragmentation effect that has already been mentioned by other posters.

The 62gr round is currently in use as it has better armour piercing capabilities than the 55gr round. The 55gr round was also easily deflected by light cover, even heavy grass in some reports, causing big problems in accuracy.

5.56mm is not the best man-stopper available, but it is what we've got. The 62gr SS109 round is a good compromise considering the limitations of the bullet and those set on us by the laws of armed conflict.

Originally posted by XphilesPhan
The m16 round does tumble when it enters the body as well as fragmenting and causing immense damage.

In fact, the soviets decided that this was an advantage and created the AK-74. I am not sure if it fires the same exact round, but essentially it was meant to imitate the damage caused by the 223.

No, the AK-74 fires the 5.45x39mm round. I have not heard of the 5.45 fragmenting, but it tumbles tremendously. The tip of the bullet has a hollow space underneath the jacket on the tip of the bullet, and thus the center of gravity is toward the rear of the bullet. When the bullet strikes something denser than air, like a human body, the rear tumbles end over end.

I have an AK-74 with the siderail scope mount. I just need to get a scope for it...

The 5.45 is the Soviet "response" to the .223/5.56, but they are not interchangeable.

The 5.45x39 is good against soft targets (people), but the 7.62x39 is better against hard targets (non-armoured vechicles).

how many of you actually have used this round on the battlefield to see its affect? your match ammo and ballistic gel tests are good in all but you have to look at the overall picture. if i can carry 210 rds of 5.56 with ten of my buddies carrying the same or i can carry 150 rounds of 7.62, which do you think would be more effective in combat? im gonna go with the weapon that has less recoil and you can put down alot more suppressive fire. the bullets do "tumbl"e before hitting an object, its plain physics. a persons reaction after getting shot depends on alot of factors not just bullet size. i can shoot someone in the ankle with a 22 and they will fall down, doesnt mean it was affective. if you hit someone in the guts with a 7.63, they might still stay standing. even better statistic, 99.999 percent of bullets shot at the enemy dont even hit the enemy so it doesnt really matter what they do out the barrel if there not hitting there target.

As has been stated the main reason for the stability factor is better accuracy... thats why the prototype X-16 wasnt adopted.... It couldnt reach army long range standards in very cold conditions. That never made sense to me because the whole development of the rifle was based upon the Vietnam War. If they wanted a long range rifle they should have stuck with the M-14. We should still be using .30-06 or .308 as our main battle rifle. The idea of wounding soliders to force others to tend to them is great but we dont fight those type of wars any more

IF the bullet does tumble, it creates a devastating wound that stops men quite readily. The problem is that with the 14.5" barrel of the M4 and the heavier, 62 gr, steel tipped bullet, the velocity is too low to get the bullet to tumble with any reliability, beyond 50m or so. The 62 gr load was created for use in the belt fed M249, to satisfy a Nato requirement of peircing both sides of a GI steel helmet at 1/2 mile. No, the bullets do NOT tumble in the air, if they did, no accuracy could be had at all. you';d miss the torso at a mere 10 yds! It was the HAGUE convention, ww ONE, that sought to eliminated soft and hollowpoint bullets. we never signed it. The Geneva Convention, ww2, said nothing about such things. The US never signed the Hague, anyway and both it and the Geneva Protocols only apply to SIGNATORY nations, in DECLARED was. The military uses fmj "ball" ammo; because it's cheaper and more reliable than softpoints. Civilians, however, should stick to Nosler 60 gr Partition softpoints, they are the best manstoppers and deer loads for 223. Black Hills loads these bullets, or you can handload them.