Mixing It With The M16

The American infantry who fought in Operation Desert Storm were armed with the M16A2 rifle. This is a modified version of the rifle used in Vietnam and supplied to armies all over the world. Manmy British units have used the M16, from the jungles of Borneo to the Falklands and Northern Ireland. Wherever soldiers needed a lightweight but accurate weapon, the M16 has been a natural choice.

The M16 was developed from the AR-10, a revolutionary weapon built with extensive use of plastics and alloys. The designers modified the AR-10 at the Army's request, and the result was the Ar-15. Firing a new 5.56-mm cartridge, it was a far cry from the US Army's existing weapons. But in 1959 the Army lost interest and turned instead to a new development programme, the 6-mm SPIW (Special Purpose Individual Weapon)(.

Airfield defence
That might have been the end of the story but for the US Air Force, who were 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. Shortly after this it was issued to guards in Vietnam. The ARVN (Army of the Republic of Vietnam) saw them, thought that they would be ideal for their small-statured men, and asked for some to be supplied by the USA. One thousand were sent out in 1962, and it became highly popular.

New interest

The US Army decided to get in on the act; the 6-mm SPIW programme was a failure, and interest returned to the AR-15. In 1963 85,000 rifles were ordered for the Army and another 19,000 for the Air Force.

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 breech 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; this was because the US ammunition factories changed the propellant powder without troubling to tell anyone. The new propellant caused much more fouling, compounded by idleness on the part of soldiers who didn't bother to clean the rifle.

Piping the gas

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 operation 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 b ackwards 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 collect a new round from the magazine and reload.

Foul gas

During the backward stroke a hammer hand 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. Some education of the troops, prolific issue of cleaning kit, and modification to the propellant cleared up that problem, and since then the M16 has been trouble-free.

Minor improvements

In 1985 the M16A2 was app-roved. This tidied up one or two minor details which experience had shown needed aqttention. The flash hider, for example, had a slot in the bottom which 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.

The US Army started by trying to find a weapon which would do the job without needing any skill from the man holding it; they asked the wrong question. What they have finished up with is an accurate and reliab le rifle which is virtually the world standard in its calibre; they got the right answer.