The M16 is a 5.56mm automatic rifle based off of the ArmaLite AR-15. Deployed in 1964 for jungle warfare during the Vietnam War, the M16A1 later replaced the M14 rifle in 1969 as the standard service rifle for the U.S military. Its improvements included a bolt-assist, chrome-plated bore, and a 30-round magazine.
With a rotating bolt, the M16 is a lightweight air-cooled, gas-operated, magazine-fed assault rifle. The M16A1 is essentially the same weapon as the M16 with the addition of forward assist and corresponding notches in the bolt carrier. It was finalized in 1967 and was produced until 1982. While no longer active in the U.S service, it is standard issue in other world armies.