Despite repeated denials, the Pentagon reversed itself last week and admitted publicly that its new lightweight rifle, the M16, does indeed have jamming troubles beyond those caused by lack of proper maintenance by G.I.s (TIME, June 9). Though the jamming is less severe than some of the rifle's critics claimed, its malfunction is serious enough for the Defense Department to order modification of all of the services' rifles, including approximately 135,000 in Viet Nam, where it is the basic infantry weapon.
The root of the trouble is the powder for the M-16's .233-cal. ammunition.
Small but magnum-loaded, the round is one of the most cantankerous in the history of American small-arms. Since 1964, when the Army was informed that Du Pont could not mass-produce the nitrocellulose-based powder within the specifications demanded by the M16, Olin Mathieson Company has supplied most ammunition for the rifle with a high-performance ball propellant of nitrocellulose and nitroglycerine.
Known as Olin WC 846, the new powder is capable of firing an M-16 round at the desired 3,300 ft. per sec. and has unexpectedly increased the rifle's automatic rate of fire from about 850 shots a minute to 1,000. The result is that the "little black rifle," as the M-16 is fearfully called by the Viet Cong, tends to jam because the powder leaves behind a dirty residue that clogs the faster-moving automatic parts.
To solve the problem, the Army for the past nine months has been outfit ting all M-16s with a new buffer system that slows the rate of fire back to 650 to 850 bullets per minute, thereby reducing the propensity to jam. In closerange fighting, a jam can be fatal. Tests with the WC 846 ball propellant show that a buffer-equipped M-16 now jams approximately only once every 4,000 shots. According to the Army's criteria, one jam every 1,001 rounds is acceptable. To compensate for the debris left behind by the new powder, all M-16s now being produced have chromium-plated chambers that are less likely to cause jamming and are easier to keep clean.
Generally, the M-16 rates high praise from the men in Viet Nam, who find its light weight (7.6 Ibs.) and rapid rate of fire ideal for jungle warfare. With proper maintenance, which will always be necessary to prevent jamming, the fighting men in Viet Nam should also find it a lethally reliable friend in need.