 The E-3, E-4 and E-7s retained the fuselage armament of the E-1 but replaced the MG 17 wing guns with two 20 mm cannons, one in each wing with 60 rpg; either MG FFs (E-3) or the more advanced MG FF/M (E-4 and E-7) that could fire the new German Mine shell ammunition.Although the explosive shells had greater destructive power than the bullets of the Brownings, these cannon's low muzzle velocity and the limited ammunition capacity of their drum magazines meant that the armament was not markedly superior to the RAF fighter's eight machine guns.Three or four hits from the cannons were usually enough to bring down an enemy fighter and, even if the fighter was able to return to base, it would often be written off.