The M16 rifle (officially designated Rifle, Caliber 5.56 mm, M16) is a family of
military rifles adapted from the
ArmaLite AR-15 rifle for the
United States military
The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is ...
. The original M16 rifle was a
5.56×45mm automatic rifle
An automatic rifle is a type of autoloading rifle that is capable of fully automatic fire. Automatic rifles are generally select-fire weapons capable of firing in semi-automatic and automatic firing modes (some automatic rifles are capable o ...
with a 20-round magazine.
In 1964, the M16 entered US military service and the following year was deployed for
jungle warfare operations during the
Vietnam War
The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...
.
In 1969, the M16A1 replaced the
M14 rifle
The M14 rifle, officially the United States Rifle, Caliber 7.62 mm, M14, is an American selective fire battle rifle chambered for the 7.62×51mm NATO (.308 in) cartridge. It became the standard-issue rifle for the U.S. military in 1959, ...
to become the US military's standard
service rifle.
[Urdang, p. 801.] The M16A1 incorporated numerous modifications including a bolt-assist, chrome-plated bore, protective reinforcement around the magazine release, and revised flash hider.
In 1983, the
US Marine Corps adopted the M16A2 rifle and the
US Army
The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, c ...
adopted it in 1986. The M16A2 fires the improved 5.56×45mm (M855/SS109) cartridge and has a newer adjustable rear sight, case deflector, heavy barrel, improved
handguard, pistol grip and
buttstock
A gunstock or often simply stock, the back po