English: M16 variants. Cut-away M16A1 (semi-auto replica lower receiver) with 20-round magazine and standard M16A2 (semi-auto lower receiver) with 30-round magazine. These rifles feature a "straight-line" recoil configuration. This layout places both the center of gravity and the position of the shoulder stock nearly in line with the longitudinal axis of the barrel bore, a feature increasing controllability during burst or automatic fire.