The MG FF/M, used in the Bf 109E-4, was modified to fire the more destructive, high-capacity mine-shells propelling the lighter shells at greater velocities than the MG FF. The early shells of this type had contact fusing, detonating on contact with the skin of the airframe rather than penetrating, then exploding. The more streamlined Bf 109 F-1, issued in small numbers starting in October, carried two cowl MG-17s and a single 20mm MG FF/M in the fuselage as an engine-mounted "Motorkanone", firing through the propeller hub.