Ballistics - Involving the AK

[Gabe Suarez]

From Fackler:

Soviet 7.62x39mm - The Soviet AK-47 Kalashnikov fires a full-metal-jacketed, boat-tail bullet that has a copper-plated steel jacket, a large steel core, and some lead between the two. In tissue, this bullet typically travels for about 26cm point-forward before beginning significant yaw. This author observed, on many occasions, the damage pattern shown in Fig. 2 while treating battle casualties in Da Nang, Vietnam (1968). The typical path through the abdomen caused minimal disruption; holes in organs were similar to those caused by a non-hollow-point handgun bullet. The average uncomplicated thigh wound was about what one would expect from a low-powered handgun: a small, punctate entrance and exit wound with minimal intervening muscle disruption.

Gabe's notes - Notice how this involves "steel core" bullets. These are not available today and are not the typical stuff from Wolf or Brown Bear.

Yugoslav 7.62x39mm - The Yugoslav copper-jacketed, lead-core, flat-base bullet, even when fired from the same Kalashnikov assault rifle, acts very differently in tissue. It typically travels point-forward for only about 9cm before yawing.Due to the lead core, this bullet flattens somewhat as it yaws, squeezing a few small lead fragments out at its open base, but this does not add significantly to its wounding potential. Referring to the wound profile of the Soviet AK-47 bullet (Fig. 2) and blotting out the first 17cm of the projectile path will leave a good approximation of what one might expect from this bullet.

Since this bullet would be travelling sideways through most of its path in an abdominal wound, it would be expected to cut a swath over three times the dimension made by the bullet travelling point forward. In addition to the larger hole in organs from the sideways-travelling bullet, the tissue surrounding the bullet path will be stretched considerably from temporary cavitation. Actual damage from the stretch of cavitation can vary from an almost explosive effect, widely splitting a solid organ such as the liver, or a hollow one such as the bladder if it is full at the time it is hit, to almost no observable effect if the hollow organs (such as intestines) when hit contain little liquid and/or air. The exit wound may be punctate or oblong, depending on the bullet's orientation as it struck the abdominal wall at the exit point. The exit wound could be stellate if sufficient wounding potential remains at this point on the bullet path.

Gabe's Notes: I pulled a few 7.62x39 bullets this morning from Brown Bear (all I had left over from the AK class) and it is fairly consistent with that description - Lead Core exposed at the base of the bullet.

Soviet 5.45x39mm - This is fired from the AK-74, which is the Soviet contribution to the new generation of smaller-calibre assault rifles and which produces the wound profile seen in Fig. 3. The full metal-jacketed bullet designed for this weapon has a copper-plated steel jacket and a largely steel core, as does the bullet of its predecessor, the AK-47. A unique design feature of the AK-74, however, is an air-space (about 5mm long) inside the jacket at the bullet's tip (Fig 1). The speculation that this air-space would cause bullet deformation and fragmentation on impact proved to be unfounded, but the air-space does serve to shift the builet's centre of mass toward the rear, possibly contributing to its very early yaw. In addition, on bullet impact with tissue, the lead just behind the air-space shifts forward into this space. This shift of lead occurs asymmetrically and may be one reason for the peculiar curvature of this bullet's path in the last half of its path through tissue (Fig 3). Only in a shot with a long tissue path, like an oblique shot through the torso, would this curved path be evident; it doesn't really add anything to wounding capacity, but might cause an occasional confusing path through tissue. This bullet yaws after only about 7cm of tissue penetration, assuring an increased temporary cavity stretch disruption in a higher percentage of extremity hits; other bullets need more tissue depth to yaw and in many cases cause only minimal disruption on extremity hits.

The abdomen and thigh wounds expected from this bullet would be essentially the same as those described above for the Yugoslav variation of the AK-47 bullet.

All pointed bullets that do not deform end their tissue path travelling base first, since this puts their centre of mass forward; this is their stable attitude. The rotation imparted to the bullet by the rifled gun barrel is sufficient to force the bullet to travel point-forward in air (in properly designed weapons), but not in tissue where such factors as bullet shape and the location of centre of mass far outweigh rotation effects. The bi-lobed yaw patterns shown in the profiles of the AK-47 and the AK-74 represent what is seen in most shots. Sometimes the bullet yaws to 180°, or the base-forward position, in one cycle. These variations, along with the curvature in bullet path at or near the end of tissue path, are of far less importance than the distance the bullet travels point-forward before significant yaw begins.

US M193 5.56x45mm - This bullet is fired from the US armed forces' first-generation smaller-calibre rifle, the M16A1. The large permanent cavity it produces, shown in the wound profile (Fig. 4), 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. As shown on the wound profile, this full-metal-jacketed bullet travels point-forward in tissue for about 12cm after which it yaws to 90°, flattens, and breaks at the cannelure (groove around bullet midsection into which the cartridge neck is crimped). The bullet point flattens but remains in one piece, retaining about 60 per cent of the original bullet weight. The rear portion breaks into many fragments that penetrate up to 7cm radially from the bullet path. The temporary cavity stretch, its effect increased by perforation and weakening of the tissue by fragments, then causes a much enlarged permanent cavity by detaching tissue pieces.

The degree of bullet fragmentation decreases with increased shooting distance (as striking velocity decreases), as shown in Fig. 5. At a shooting distance over about 100m the bullet breaks at the cannelure, forming two large fragments and, at over 200m, it no longer breaks, although it continues to flatten somewhat, until 400m. This consistent change in deformation/fragmentation pattern has an important forensic application. It can be used to estimate shooting distance if the bullet is recovered in the body and has penetrated only soft tissue.

The effects of this bullet in the abdomen shot will show the temporary cavity effects as described for the Yugoslav AK-47 and, in addition, there will be an increased tissue disruption from the synergistic effect of temporary cavitation acting on tissue that has been weakened by bullet fragmentation. Instead of finding a hole consistent with the size of the bullet in hollow organs such as the intestine, we typically find a hole left by missing tissue of up to 7cm in diameter (see permanent cavity in Fig. 4).

Gabe's Note: So according to Fackler's own studies, a lead core 7.62x39 bullet will yaw sooner than a 5.56x45 (9cm as opposed to 12cm).

Hmmmmmmmmmmmmm;)

[Gabe Suarez]

According to the IWBA, “the critical minimum velocity for obtaining maximum terminal performance from .223 Remington/5.56mm ammunition is approximately 2700 fps. Bullets that are propelled below this velocity do not provide optimal terminal performance, and thus are less capable of creating wound trauma that will produce rapid incapacitation of a criminal attacker.”

This is very interesting in that most rifles intended (or marketed) for CQB purposes have barrells shorter than 20”. The IWBA goes on to explain a great deal about performance under 100 yards, “…when fired from rifles fitted with a 20-inch or longer barrel.”

But then, “Shooting the M193 or M855 from a rifle with a barrel length less than 14.5-inches produces insufficient muzzle velocity to achieve the terminal performance described above. A rifle fitted with a 14.5-inch barrel is adequate for close-quarters battle. For engagements anticipated at greater than room distance but less than 100 yards, a rifle fitted with a 16.5-inch barrel should be employed to ensure sufficient velocity.”

So in essence, these 14.5” and 16” barreled rifles are suitable for 100 yards and in. That is fine as we know much of the rifle action seen around the world centers on urban areas and 100 yards is likely the farther distances.

[Gabe Suarez]

And having said that, we can agree that any 5.56 shot out of a 16" or less barrel is fairly a 100-150 yard rifle at best in terms of ballistic effect.

Hitting paper or stell at 400m is irrelevant to me. It is what the bullet will do once it hits that matters.

So if you have a bullet like the 7.62x39mm, that will yaw sooner than the 5.56 (9cm rather than 12cm), and penetrate hard cover and brush much better than the 5.56, why on earth would we choose the 5.56 over the lead core 7.62x39mm?

Ok.....this is going to be a hot one.;)

[Gabe Suarez]

This is the pulled bullet from he Brown Bear 7.62x39 123 grain HP (AB762HP)

[Al Lipscomb]

The rather interesting nature of the 5.56 fragmentation has been a source of arguments among its users for many years. Reports of horrible wounds from one soldier are compared with accounts of tiny holes that seemed to do little damage from another. Velocity and thinkness of tissue being critical for fragmentation to become a factor.

Of the current brands of AK ammunition, I believe that the Winchester rounds are given the best marks for wounding. I am not sure I would get too caught up in the difference between it and the Bear.

[S-Lee]

a 7.62x39 soft point round are like a 30-30. It is a man killer that is superior to anything 5.56 can provide....but that is a well loaded SP like Laupa or Winchester. the Wolf and the likes are not consistant in accuracy.

the 5.56 not only yaw, it also breaks apart, which are very destructive. but you are right, it really depands on the velocity.

here is a break down of the said velocity.
the magic number here is 2700fps...
M193
20" barrel - 190-200m -
16" barrel -140-150m
14.5" barrel - 95-100m
10.5" CQB-R - 40-45m

M855
140-150m
90-95m
45-50m
12-15m

You can see why the M855 are ineffective at longer distance and just punching holes through the target. M855 was never designed to be fired against soft tissue targets, it was design to penetrate armor at longer distance for the SAW.

[Gabe Suarez]

but that is a well loaded SP like Laupa or Winchester. the Wolf and the likes are not consistant in accuracy.

Well, I have received various student reports of very good accuracy from the Brown Bear ammo. I can only speak for myself but I have had no problems with accuracy inconsistencies out of my Fuller-bilt AKs.

Perhaps, it is time to get someone here at WT who is familiar with the IWBA testing processes and run a line of tests on CURRENT Russian ammo. Both so we know what we should choose as well as to stop relying on Vietnam era information to base our choices on.

[S-Lee]

I think the 7.62x39 with a round like the Laupa SP are great man killer, but if I am given the opportunity to select exact what i can carry to a fight, I would pick a 14inch M4 system with 6.8OTM. this round would be as effective as a 7.62x39 in soft tip and have all the egronomics benefit of the M16 system. If you want ultimate performance, then get a gas piston upper from LWRC in 6.8.

with the possibilities of HK releasing the 416 and the 417 anfd also the 418 in 6.8, and also FN SCAR-L which will also carry the 6.8, you can have your cake and eat it too.

[Al Lipscomb]

I have some of the Winchester ammo that I keep in the magazines in the gun case with my AK. These would be the first to be loaded if I had to grab that gun. The rest of the mags in my rifle BOB are all loaded with Wolf.

The accuracy for any of the rounds have always been beyond my skill set as a shooter in a standing position. Like many things I have to compromise to meet as many of my goals as possible within my budget. For the inital engagement in a SD situation I have the best ammunition I can obtain, the Winchester JSP. If I find myself on the third magazine (30 round magazines), I am into the military surplus.

I am pretty sure the data on the rounds is pretty recent. It was not that long ago that Dr. Roberts tested the Winchester ammunition.

[georgel]

While I'm still an AR user, it's primarily a logistical/resources issue, I've always thought the M4 barrel length was a mistake. Per a discussion this weekend, I've been told it was a convience issue for ease of use in confined spaces. 16" barrel were already on the edge as expounded by Gabe's resouces.
Looked at AKs this weekend. Probably going for an M70AB2 Yugo when the money frees up. Meanwhile, I'm still investing in the AR platform.:D