The M1 Abrams (/ˈeɪbrəmz/)[7] is a third-generation American main battle tank designed by Chrysler Defense (now General Dynamics Land Systems)[8] and named for General Creighton Abrams. Conceived for modern armored ground warfare and now one of the heaviest tanks in service at nearly 68 short tons (62 metric tons), it introduced several modern technologies to US armored forces, including a multifuel turbine engine, sophisticated Chobham composite armor, a computer fire control system, separate ammunition storage in a blow-out compartment, and NBC protection for crew safety. Initial models of the M1 were armed with a 105 mm M68 gun, while later variants feature a license-produced Rheinmetall 120 mm L/44.