Production of the new Alkan-Hamy synchronization gear permitted the wing-mounted Lewis gun on the earliest examples to be replaced with a synchronised Vickers gun mounted on the fuselage to fire through the propeller arc. The standard Royal Flying Corps synchroniser, the Vickers-Challenger gear, was unreliable and unpopular with pilots, so that in British service the over-wing Lewis gun was retained. The Lewis gun was fitted to the new Foster mounting, a curved metal rail which allowed the pilot to slide the gun back to change ammunition drums and to clear jams. Pilots could also aim the gun upwards to shoot into the underside of aircraft above which was used to good effect by several ace pilots.