M16A1

The M16A1 is a military rifle and the first major revision of the original AR-15/M16 platform used by the United States. It was adopted in 1967 and served as the standard-issue infantry rifle in Vietnam and beyond, replacing earlier M16 configurations before being superseded by later variants. It was produced by Colt and other licensed manufacturers for U.S. and allied forces.

Technical characteristics: The M16A1 is a gas-operated, air-cooled, internally selective-fire rifle chambered for 5.56x45mm NATO, fed from 20-round detachable magazines. It features a 20-inch barrel, direct gas impingement operation, and a chrome-lined bore and chamber intended to improve durability and ease of cleaning. The fixed iron sights are mounted on the carrying handle of the upper receiver.

Improvements over earlier versions: The A1 introduced a forward assist to help close the bolt, a redesigned front sight/gas block arrangement, and enhanced internal parts and feed ramps to increase reliability under adverse conditions. The overall layout and field service remained consistent with Vietnam-era usage, with the familiar stock and carrying handle.

Operational history and legacy: The M16A1 saw extensive combat service in Vietnam and was widely exported to allied nations. It remained the U.S. Army's standard rifle into the early 1980s, before the fielding of the M16A2, and it continued in various roles for years thereafter. It is regarded as a bridge between the original AR-15/M16 and later 5.56mm systems.