 For example, on 18 August a brand new Spitfire of 602 Squadron was hit by 20 mm shells which exploded in the structure of the rear fuselage.Although the crippled aircraft was successfully landed back at its airfield it was subsequently deemed to be unrepairable.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.