TheM16 rifle, officially designatedRifle, Caliber 5.56 mm, M16, is a family ofmilitary riflesadapted from theArmaLite AR-15rifle for theUnited States military. The original M16 rifle was a5.56mmautomatic riflewith a 20-round magazine.
In 1964, the M16 entered US military service and the following year was deployed forjungle warfareoperations during theVietnam War.In 1969, the M16A1 replaced theM14 rifleto become the US military’s standardservice rifle.The M16A1 improvements include a bolt-assist, chrome-plated bore and a 30-round magazine.
In 1983, the US Marine Corps adopted the M16A2 rifle and the US Army adopted it in 1986. The M16A2 fires the improved5.56×45mm NATO(M855/SS109) cartridge and has a newer adjustable rear sight, case deflector, heavy barrel, improvedhandguard, pistol grip andbuttstock, as well as a semi-auto and three-round burst fire selector.Adopted in July 1997, the M16A4 is the fourth generation of the M16 series. It is equipped with a removable carrying handle andPicatinny railfor mounting optics and other ancillary devices.
The M16 has also been widely adopted by other armed forces around the world. Total worldwide production of M16s is approximately 8 million, making it the most-produced firearm of its 5.56 mm caliber.TheUS militaryhas largely replaced the M16 in frontline combat units with a shorter and lighter version, theM4 carbine.