The primary mission of the Defiant was the destruction of incoming enemy bombers. The principal armament of the aircraft is its powered dorsal turret, equipped with four 0.303 in (7.7 mm) Browning machine guns. The fuselage was fitted with aerodynamic fairings that helped mitigate the drag of the turret; they were pneumatically powered and could be lowered into the fuselage so that the turret could rotate freely. The Brownings were electrically fired and insulated cut-off points in the turret ring prevented the guns firing when they were pointing at the propeller disc or tailplane. The gunner could rotate the turret directly forward and transfer firing control of the guns to the pilot, with the guns firing along each side of the cockpit canopy; this was rarely done as the turret's minimum forward elevation was 19° and the pilot did not have a gunsight, possibly because the Defiant was outfitted to perform zero deflection shooting, as were several contemporaneous designs arising from Air Ministry specifications.