The M16, formally the United States Rifle, Caliber 5.56 mm, M16, is an assault rifle developed by Eugene Stoner. The rifle is based on the ArmaLite AR-15 series of rifles. The M16 was originally designed for US soldiers as a replacement for the M14 automatic rifle.
Unfortunately, many problems with the M16 were exposed during the Vietnam war. Due to problems associated with IMR rifle powder, M16's were prone to jamming, and had notoriously bad firing consistency. The problems were rectified after Congressional inquiries. The M-16 carbine used in Vietnam was called the "XM-177". Recent remodels of the M16 has yielded the M16A2, M16A3, and the M16A4, which have corrected the many problems that their predecessor encountered.
See also: AK-47.