The mentioned high lethality of the AR-15 rifle is still a subject of much contention. However, in this early report, the terminal effects of the rifle are described with considerable reverence by RVNAF commanders and their US advisors in the ARPA report:

(1) (C) “On 160900 June 62, one platoon from the 340 Ranger Company was on an operation vic. YT260750 and contacted 3 armed VC in heavily forested jungle. Two VC had carbines, grenades, mines, and one had a 4 ANNEX “A” CONFIDENTIALCONFIDENTIAL SMG. At a distance of approximately 15 meters, one Ranger fired an AR-15 full automatic hitting one VC with 3 rounds with the first burst. One round in the head-took it completely off. Another in the right arm, took it completely off, too. One round hit him in the right side, causing a hole about five inches in diameter. It cannot be determined which round killed the VC but it can be assumed that any one of the three would have caused death.

…

(2.) (C) “On 9 June a Ranger Platoon from the 40th nf Regt was given the mission of ambushing an estimated VC Company. The details are as follows: a. Number of VC killed: 5 b. Number of AR-15’s employed: 5 c. Range of engagement: 30-100 meters d. Type wounds: 1. Back wound, which caused the thoracic cavity to explode. 2. Stomach wound, which caused the abdominal cavity to explode. 3. Buttock wound, which destroyed all tissue of both buttocks. 4. Chest wound from right to left, destroyed the thoracic cavity. 5. Heel wound, the projectile entered the bottom of the right foot causing the leg to split from the foot to the hip. These deaths were inflicted by the AR-15 and all were instantaneous except the buttock wound. He lived approximately five minutes.

…

Five VC were hit, all five with body wounds, and all five killed. Four were probably killing wounds with any weapon listed, but the fifth was essentially a flesh wound. The AR-15 made it a fatal wound.

…

(9.) (C) “On 13 April, 62, a Special Forces team made a raid on a small village. In the raid, seven VC were killed. Two were killed by AR-15 fire. Range was 50 meters. One man was hit in the head; it looked like it exploded. A second man was hit in the chest,; his back was one big hole. ” (VN Special Forces)

It’s tempting to dismiss reports this dramatic as simply exaggerated hearsay, but I do not. Naturally, these anecdotes do not make a solid and rigorous case for the .223 round having magical killing ability – only laboratory tests could do that – but I do believe they actually happened. I find it difficult to believe that the Rangers and Green Berets quoted were mistaken, and terminal effects such as they describe are possible with hits from the .223 caliber, and have been documented in other cases. When viewing pictures of some very grievous wounds caused by the 5.56mm caliber, “exploded” is definitely a word that comes to mind.



This tempers the current view of 5.56mm effectiveness, broadly speaking. The ammunition used when the ARPA report was being written were pre-M193 specification, but were broadly similar to that round, except for having a somewhat better ballistic coefficient. The terminal effects of Belgian-designed M855 ammunition are comparable to this ammunition, too, meaning there is little reason to expect anything to have changed in this regard.

It makes sense, then, that M855 has not been characterized in official reports as a “poor” terminal performer, but an “inconsistent” one; this is precisely the result we’d expect to see for a round with generally good yaw characteristics but still totally subject to the fleet yaw problem. Still, the conclusion that results like those in the ARPA report are possible – or even likely – does not seem like a misguided one to me.

- See more at: http://www.thefirearmblog.com/blog/2015/02/13/weekly-dtic-ar-15-vietnam-1962/#sthash.BLxWr8r9.dpuf