The AR-15 is the semiautomatic version of the M16 series of assault rifles, designed by the great designer
Eugene Stoner, and it is most commonly used by the US armed forces. I would get into the history of this gun, but it is very
longwinded but thoroughly interesting. AR-15s are usually chambered in 5.56 x 45mm (.223 Remington) caliber and have either 24", 20", 16", or 11.5" barrels and have either collapsible stocks or full stocks and may either have a NATO railed
flattop or a carrt handle with an adjustable rear sight. This weapon has been the basis of numerous high-accuracy rifles.