KCI USA Magazine, 30 Carbine, 30 Rounds, Fits M1 Carbine, Black KCI-MZ026 Designed to fit your M1 Carbine chambered in .30 Carbine" this magazine provides smooth and reliable feeding. Constructed of steel with an electroplated finish" using a high-tensile strength compression spring and a bolt hold-open follower provides for long and reliable life.