British (7.7 mm) Vickers machine gun machine guns mounted in the cowl, firing forward through the propeller disc.

External differences included better streamlining of the forward fuselage and a synchronised machine gun mounted on the upper fuselage and firing through the propeller disc.

Halfway through the turn, something glistened through the bottom edge of his propeller disc.

Something rattled and thumped like a runaway donkey-engine: bullet-streams raced above his head, flickering past the propeller disc.

Designed as a fighter, a Lewis machine gun was installed above the pilot, placed above the propeller disc, with an eye level sight.

When an aircraft is in straight and level flight at cruise speed, the propeller disc is perpendicular to the relative wind.

This asymmetry displaces the center of thrust of the propeller disc towards the blade with increased thrust.

Considering right-hand tractor engines (lines projecting from propeller discs represent the p-factor induced thrust lines):

The MG 131 fired electrically primed ammunition in order to sustain a high rate of fire when shooting through the propeller disc of a single-engined fighter.

It differed, however, in having an even shorter forward fuselage, so that the nose of the aircraft was now behind the propeller discs.