By Hilton Hamann

From PARATUS, April 1991, pp. 36 - 38. (PART TWO)

This bullet is fired from the US armed forces' first generation smaller-calibre rifle, the M16Al. The large permanent cavity it produces, shown in the wound profile (Fig 3). 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 degrees, 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% 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 in. creased 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 3. 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 3.)

The thigh entrance wound will be small and punctuate. The first part of the tissue path will show minimal disruption, The exit will vary from the small punctate hole described for the Soviet AK-47 to the stellate exit described for the Yugoslav AK-47, depending on how thick the thigh is and where the bullet perforates. In a sufficiently thick thigh, the M193 bullet fragmentation is also likely to cause a significant loss of tissue arid probably one or more small exit wounds near the large stellate one.

(Editor's note: The South African R4 and R5 bullet probably closely resembles this round).

The slightly longer and heavier American M855 bullet shot from the M16A2 assault rifle is replacing the M193 bullet shot from the M16A1 as the standard bullet of the US armed forces.

FN Herstal originally developed this bullet type (which has a steel "penetrator" as the forward part of its core) designating its bullet the SS109. The wound profile is very similar to that produced by the M 1 93 bullet.

Although the SS109 and M855 are not the same bullet, their differences are small and one almost needs a magnifying glass and a side-by-side comparison to differentiate the two. There is little difference in their performance in tissue.

The abdominal and thigh wound produced by the M855 or the SS109 bullets would essentially be the same as those described above for the M16A1 M193 bullet.

The longer 5,56mm bullets (M855, SS109) need a higher relational velocity to maintain stabilization in air. FN claimed that this faster rotation also causes the SS109 to have a significantly longer path in tissue before marked yaw occurs, thus producing wounds of less severity. This is simply untrue (compare Fig 3 with Fig 4). Additional rotation beyond that needed to keep the bullet straight in air appears to have little or no effect on the projectile's behaviour in tissue.

However, there is a situation concerning rotation rates whereby these longer 5,56mm bullets can cause increased wound severity. Shooting the SS109 or M855 in the older M16A1 rifle (they are not intended for use in this 1-in-12in. twist barrel, but iii the newer l-in-7in, twist) produces a bullet spin rate insufficient to stabilise the longer bullets. Such a bullet will yaw up to 70 degrees in its path through air. Striking at this high yaw angle (essentially travelling sideways), these bullets break on contact and the marked fragmentation, acting in synergy with the temporary cavity stretch, causes a large (over 15cm) stellate wound with the loss of considerable tissue.

The wound profile of this full-metal-jacketed military bullet (Fig 5) shows the characteristic behaviour in tissue observed in all non-deforming pointed bullets. It yaws first through 90 degrees and then, after reaching the base forward position, continues the rest of its path with little or no yaw.

The uncomplicated thigh wound might show very minimal tissue disruption since the streamlined bullet tends to travel point forward during the first 16cm of its tissue path. The abdominal wound, with a sufficiently long path so that the bullet will yaw, causing the large temporary cavity that is seen at depths of 20 to 35cm, would be expected to be very disruptive. If the bullet path is such that this temporary cavity occurs in the liver, this amount of tissue disruption is likely to make survival improbable.

The design standards for ammunition that can be called "NATO" ammunition do not specify the bullet jacket material or jacket thickness.

The construction of the West German 7.62 NATO bullet differs from the US 7.62 NATO round in that the jacket material is copperplated steel, whereas the US version is copper (or the so-called gilding metal alloy, which is predominantly copper).

The West German steel jacket is about 0.020in (0.5i-nm) thick near the cannelure and the US copper jacket is about 0-032in (0.8mm) thick at the same point. This design difference is responsible for a vast difference in performance in tissue.

The German bullet after travelling point-forward for only about 8cm, yaws and breaks at the cannelure. The flattened point section retains only about 55% of the bullet's weight, the remaining 45% becomes fragments.

The wound profile can be described as an enlarged M16 profile with dimensions of the tissue disruption increased by 60 percent (temporary cavity about 22cm diameter; permanent cavity about 11 cm diameter, penetration depth of the bullet point about 58cm). The uncomplicated thigh wound from the bullet is likely to have a large exit with the loss of substantial tissue near the exit; still this might not be a very serious wound since the bullet fragmentation does not occur until beyond 10cm of penetration depth and, in most shots, the bullet will have passed well beyond the major vessels before this occurs.

The abdomen shot, however, because of the much enlarged permanent cavity from bullet fragmentation, is likely to prove fatal in a majority of cases.

(Editor's note: The South African R l bullet probably displays performance similar to the US version of the NATO 7,62mm bullet).

This bullet, although not nearly as common as the AK-47 or the others discussed above, is included because it is currently used in the Dragunov sniper rifle and the Communist bloc light machine-guns. Also, since it was the standard Soviet military round in WW1 and WW2 (in the bolt action Mosin-Nagant), it might well be found in considerable numbers in some Third World Countries. The bullet weighs 9.6 grams; the base is hollowed out with a cone-shaped cavity - 5mm deep for the Soviet, 3mm deep for the Chinese. The Soviet bullet has a copper-plated steel jacket and the Chinese one has a jacket of what appears to be brass. The muzzle velocity is about 853m/s and the wound profile closely resembles that of the 7.62 NATO (US version). Thigh and abdominal shots would thus be as described above for the US 7.62 NATO bullet.

In addition to the full-metal-jacketed construction which makes them "military" bullets, the pointed ogival "spitzer" tip shape is shared by all modern military bullets.

The obvious advantage of this streamlined shape is decreased air drag, allowing the bullet to retain velocity better for improved long-range performance. A modern military 7,62mm bullet (with all lead core) will lose only about one-third of its muzzle velocity over 500 yards (457m); the same weight bullet with a round-nose shape loses more than one-half of its velocity over the same distance.

More pertinent to the present discussion is this pointed shape's effect on the bullet's yaw in tissue. The first full-metal-jacketed bullets (1885-1910) were over four calibers long and round nosed. Typical of this bullet type are the 6.5mm Carcano and 30-40 Krag bullets; (Editor's note: Early.303 Enfield and Mauser bullets of various calibers used in the British Empire and in South Africa match the above description) they penetrate tissue simulant travelling point forward for 50cm or more before significant yaw begins.

The very minimal wounding effect produced by these early round-nosed, jacketed bullets was remarked upon by surgeons of the time. Even those soldiers with through-and-through chest wounds in which the bullet missed the large vessels (but passed through the lung) would be fit to rejoin their units in a few weeks.

The distance that the military type bullet travels point-forward before yawing is critical to wounding effects. The distance shown on the wound profiles is the average distance at which this occurs. However, it is important to recognise how much shot-to-shot variation from this average distance can be expected.

Taking the M16 wound profile as an example, it shows significant yaw starting at a 12cm penetration depth. Seven out of ten shots can be expected to yaw within 25 percent of this distance (between nine and 15cm penetration depth). This plus or minus 25 percent rule is a useful approximation that can be applied to other wound profiles.

Let us apply it to the 50cm distance-to-yaw for the older bullets; whether the bullet begins to yaw between 37 or 63cm penetration distance does not effect most wounds of the human body because in the great majority of cases the total tissue path will be less than 37cm.

Conversely, inconsistent effects have been noted in wounds caused by the M16 and other modern military bullets. Considering the variation in length of the possible tissue path through the human body, this "inconsistency" of effect is to be expected. Beware! This variation can be used to dupe the unsuspecting. A series of shots through a 14 or 15cm block of tissue simulant or the leg of a 25kg animal can give enough variation so that, by selective choice of exit wound photographs, one can "prove" any point one wishes (such as one bullet being more humane than another).

The author hopes that understanding this will make the reader less likely prey to this sort of deception.

Bullet mass and bullet striking velocity establish a bullet’s potential: they set the limit on the tissue disruption it can produce. Bullet shape and construction determine how much of this potential is actually used to disrupt tissue; they are the major determinants of bullet effect.

Far and away the most disruptive bullet of those described is the German 7,62 NATO round. Its fragmenting behaviour maximises utilisation of its much higher potential (bullet mass well over twice that of any of the 5,56mm bullets and velocity only ten percent less than theirs) for tissue disruption.

The author (Fackler) has not tested other European 7,62 NATO rounds, but the "NATO standards" apparently allow bullet designers great latitude in the choice of bullet jacket material and thickness.

In 1979 a published high-speed x-ray photograph showed the Swedish 7,62mm equivalent to the 7,62mm NATO bullet breaking in a soap block shot at 100m. Although bullet fragments were not recovered and photographed (the importance of bullet fragmentation in tissue disruption was not well recognised at the time), one must suspect the same very disruptive behaviour from this bullet as from the West German round.

This is particularly ironic since the Swedish wound ballistics program was using every means possible to discredit the M16 as "inhumane" while at the same time, Sweden was producing a 7,62mm military bullet that caused far more extensive wounds than the M16.

What Dr Fackler has done in his article is to prove that the construction of a military bullet is the most important factor to be considered. His models show that the old dogma of driving the heaviest bullet at the highest velocity produces the most effective wound is still valid if the bullet is properly designed and constructed.

However, as we all know, it isn't a perfect world. You can have the best possible bullet, guaranteed to put your enemy down with a single shot, but if you can't hit him it is not worth a damn.

The most important consideration for any armed force is to optimize the hitting potential of its men, and for that, the new generation of smaller calibre assault rifles are obviously better suited.

It all boils down to the fact that the training of armed personnel is more important than the calibre of weapon with which they are equipped. If the soldier is proficient with any one of the modern assault rifles he is capable of doing the job.

I believe the R4's and R5's give him the edge.