[In November 1963, McNamara approved the Army’s order of 85,000 XM16E1s for jungle warfare operations; and to appease General LeMay, the Air Force was granted an order for another 19,000 M16s. Meanwhile, the Army carried out another project, the Small Arms Weapons Systems, on general infantry firearm needs in the immediate future. They recommended the immediate adoption of the weapon. Later that year the Air Force officially accepted their first batch as the United States Rifle, Caliber 5.56 mm, M16.
The Army immediately began to issue the XM16E1 to infantry units but the rifle was initially delivered without adequate cleaning supplies or instructions. When the M16 reached Vietnam with U.S. troops in March 1965, reports of stoppages in combat began to surface. Often the gun suffered from a stoppage known as “failure to extract,” which meant that a spent cartridge case remained lodged in the chamber after a bullet flew out the muzzle. Although the M14 featured a chrome-lined barrel and chamber to resist corrosion in combat conditions, neither the bore nor the chamber of the M16/XM16E1 was chrome-lined. Several documented accounts of troops killed by enemy fire with inoperable rifles broken-down for cleaning eventually brought a Congressional investigation.
“ We left with 72 men in our platoon and came back with 19, Believe it or not, you know what killed most of us? Our own rifle. Practically every one of our dead was found with his [M16] torn down next to him where he had been trying to fix it.
- Marine Corps Rifleman, Vietnam. ”
The root cause of the stoppages turned out to be a problem with the powder for the ammunition. In 1964 when the Army was informed that DuPont could not mass-produce the nitrocellulose-based powder to the specifications demanded by the M16, the Olin Mathieson Company provided a high-performance ball propellant of nitrocellulose and nitroglycerin. While the Olin WC 846 powder was capable of firing an M16 5.56 mm round at the desired 3,300 ft (1,000 m) per second, it had the unintended consequence of increasing the automatic rate of fire from 850 to 1000 rounds per minute. This would leave behind dirty residue, making the M16 more likely to have a stoppage. The problem was resolved by fitting the M16 with a buffer system, slowing the rate of fire back down to 650 to 850 rounds per minute and outfitting all newly produced M16s with an anti corrosive chrome-plated chamber.
On February 28, 1967, the XM16E1 was standardized as the M16A1. Major revisions to the design followed. The rifle was given a chrome-lined chamber (and later, the entire bore) to eliminate corrosion and stuck cartridges, and the rifle’s recoil mechanism was re-designed to accommodate Army-issued 5.56 mm ammunition. Rifle cleaning tools and powder solvents/lubricants were issued. Intensive training programs in weapons cleaning were instituted, and a comic book style manual was circulated among the troops to demonstrate proper maintenance. The reliability problems of the M16 diminished quickly, although the rifle’s reputation continued to suffer.](http://en.wikipedia.org/wiki/M16_rifle#M16_adoption)