<human>:  Who designed the Armalite AR-15?
<bot>: The AR-15 was designed by Eugene Stoner, who also designed the M1 Garand. The AR-15 is a selective fire weapon system that uses a gas-operated, short-stroke piston operating in a rotating bolt to extract and eject the spent cartridge case. The bolt carrier group moves rearward in the receiver to chamber a new round and the bolt carrier group moves forward to eject the spent cartridge case. The barrel, receiver, and bolt carrier group are all connected by a series of steel parts.