page_title: M16 rifle
section_title: XM16E1 and M16A1 (Colt Model 603)
hierarchical_section_title: M16 rifle / Variants / XM16E1 and M16A1 (Colt Model 603)
caption_attribution_description: An infantryman armed with an M16A1 rifle and an AN/PVS-2 Starlight scope for use at night.
context_page_description: 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 original M16 rifle was a 5.56mm automatic rifle 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. In 1969, the M16A1 replaced the M14 rifle to become the US military's standard service 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 improved 5.56×45mm NATO cartridge and has a newer adjustable rear sight, case deflector, heavy barrel, improved handguard, pistol grip and buttstock, 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 and Picatinny rail for mounting optics and other ancillary devices.
  The M16 has also been widely adopted by other armed forces around the world.
context_section_description: The U.S. Army XM16E1 was essentially the same weapon as the M16 with the addition of a forward assist and corresponding notches in the bolt carrier. The M16A1 was the finalized production model in 1967 and was produced until 1982.
  To address issues raised by the XM16E1's testing cycle, a closed, bird-cage flash suppressor replaced the XM16E1's three-pronged flash suppressor which caught on twigs and leaves. Various other changes were made after numerous problems in the field. Cleaning kits were developed and issued while barrels with chrome-plated chambers and later fully lined bores were introduced.
  With these and other changes, the malfunction rate slowly declined and new soldiers were generally unfamiliar with early problems. A rib was built into the side of the receiver on the XM16E1 to help prevent accidentally pressing the magazine release button while closing the ejection port cover. This rib was later extended on production M16A1s to help in preventing the magazine release from inadvertently being pressed. The hole in the bolt that accepts the cam pin was crimped inward on one side, in such a way that the cam pin may not be inserted with the bolt installed backwards, which would cause failures to eject until corrected. The M16A1 saw limited use in training capacities until the early 2000s, but is no longer in active service with the U.S., although is still standard issue in many world armies.
caption: A Vietnam War-era infantryman armed with an M16A1 rifle and an AN/PVS-2 Starlight scope for use at night.
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