M16/M4/AR-15 RIFLE

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.^[1]In 1969, the M16A1 replaced theM14 rifleto become the US military’s standardservice rifle.^[21][22]The M16A1 improvements include a bolt-assist, chrome-plated bore and a 30-round magazine.^[1]

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.^[23][24]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.^[25]

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.^[26]TheUS militaryhas largely replaced the M16 in frontline combat units with a shorter and lighter version, theM4 carbine.^[27][28]