The M16 rifle is one of the most popular 5.56mm caliber weapons ever produced, with over 8 million rifles manufactured, and has been popular with mostly Western militaries for over 50 years. The M16 is the official military designation for the ArmaLite AR-15 rifle invented by Eugen Stoner. The original M16 was a select-fire 5.56x45mm caliber rifle with a 20 round magazine. Introduced in 1963 into the US military it was immidiatly used in operations during the Vietnam war. In 1969 the M16A1 replaced the M14 rifle to become the standard issued US military’s service rifle. Ever since the M16 has been improving making it more reliable, user friendly, with 30 round magazines, chrome plated bore, a bolt assist and more. In 1983, the United State Marine Core adopted the M16A2 rifle version and the U.S. Army adopted it in 1986. The M16A2 improved the previous model by firing the improved 5.56×45 mm NATO (M855/SS109) cartridge, having an adjustable rear sight, case deflector, heavy barrel, improved handguard, pistol grip and buttstock, as well as a semi-auto and three-round burst only fire selector. Adopted in 1998, the M16A4 is the 4th generation of the M16 series. It is equipped with a removable carrying handle and Picatinny rail for mounting optics and other weapon accessories. The U.S. Army and USMC have largely replaced the M16 in combat units with the shorter and lighter M4 during the late 1990’s and early 2000’s. The civilian version of the M16 and M4, the AR-15 is one of the most popular civilian assault rifle in the market today with thousands of local and international manufacturers producing their own versions but all still using the basic design by Eugen Stoner.