THE M16

The Air Force was looking for a small and handy short-range weapon with which to arm airfield guards. They looked at the AR-15, liked it, and ordered 8,000 in 1962. Designated M16 by the Pentagon, the rifle was soon issued to Air Force security personnel in Vietnam. The ARVN (Army of the Republic of VietNam) saw them, thought that they would be ideal for their small-statured men, asked for some to be supplied, and were issued 1,000. The M16 was becoming increasingly popular, and the Army wanted a piece of the action. In 1963 85,000 rifles were ordered for the Army and another 19,000 for the Air Force. The first Army issues were made to Special Forces units, particularly those serving in SouthEast Asia. By the end of 1965 large-scale actions involving M16-armed GIs were taking place.

Before the Army could standardize the weapon, they insisted on some small modifications: of these, the most important was the addition of a ‘bolt closing device’. Occasionally a dirty cartridge or a dirty chamber caused the bolt to stick before being fully closed, and a positive closing plunger was added on the right-hand side of the receiver. With this, the rifle now became the M16A1 and received official blessing.

It got a semi-official cursing in Vietnam, acquiring a terrible reputation for stoppages and jams in action. Early reports indicated that the M16 was jamming solid as a result of excessive fouling. These reports grew in volume and regularity to the extent that a special Congressional Investigation Board was established over and above the inquiry set up by the Army. Congress went into the affair with great application and it was the Board’s final report that set out the whole sorry tale. By the mi-1960s, the US government had taken the whole affair out of the hands of the military, which nevertheless continued its own investigations and set up its own inquiry board. Many of the civilians involved were ex-military men who were horrified at what they uncovered:

When the initial AR-15 trials were being carried out commercial ammunition was used, and all went well. The commercial ammunition was based on a propellant known as IMR (improved military rifle), which had been in use for many years. When fired in the 5.56-mm cartridge it presented no problems, burning cleanly and reliably. Most of the early trial's ammunition and early batches of service ammunition used this type of propellant. Indeed, when the rifle was issued to the troops they were told that the M16 was so efficient and to that it would never require cleaning. Exactly where this idea originated is now impossible to determine, but needless to say the troops were happy to accept it at face value. When combined with another, unsuspected factor, failures became inevitable. The unsuspected factor was that the ammunition specification had been changed without anyone being told.

They were shown M16 rifles that were covered in dirt and rust as well as examples clogged solid with fouling. It was not long before the ammunition change was discovered. What had happened was simple. The demands of an ever-growing Vietnam involvement had outstripped the abilities of the American ammunition suppliers to keep filling the 5.56-mm cartridges with the satisfactory IMR propellant. Ball powder had been substituted, but somewhere along the line this information had been ‘lost’. Full trials had not been carried out on the effects of the new ball powder and the troops in the field had to discover it the hard way. Not only did the ball powder burn leaving carbon and other deposits, but it burned faster, which increased the rate of fire of the M16 beyond a safe limit. This explained other reports that many components were breaking long before they should have.

The reason the powder caused problems was tied in with the peculiar method of operation of the M16. Most gas-operated weapons tap gas from the barrel into a cylinder, where it drives a piston backwards to operate the bolt. But the M16 simplified things by simply piping the gas back and allowing it to hit the bolt carrier and, literally, blast it back. The carrier moved backwards and a curved slot, holding a lug on the bolt, caused the bolt to revolve and unlock from the chamber, after which the carrier pulled the bolt back and ejected the spent case. Two springs then propelled the bolt forward again to cleat a new round from the magazine and re-load. During the backward strode a hammer had been cocked, and a fresh pull on the trigger now fired the next round. Automatic fire was achieved by the bolt carrier tripping the sear as the bolt finally closed, and so squirting the bolt carrier full of fouling-laden gas was bound to cause problems.

Corrective measures proved simple, though laborious. Some education of the troops, prolific issue of cleaning kit, and modification to the propellant cleared up any difficulty, and since then the M16 has been trouble-free.

In 1985 the M16A2 was approved. This tidied up one or two minor details which experience had shown needed attention. The flash hider, for example, had a slot in the bottom that allowed gas to blast down from the muzzle and kick up dust, revealing your position and obscuring your view; so this slot has been done away with. A new barrel, matched to the harder-hitting SS109 round, has been developed. Although the M16A2 can be ordered with a full-auto option, the first service examples fire three-round bursts and semi-auto, which allows for much more-accurate and effective fire at longer ranges than was possible with the original version.