Ballistics - Involving the AK
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).
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