Bristol Beaufighter Mk V
Two Beaufighter Mark IIFs were converted to Mark Vs by having one pair of cannons and the wing-mounted machine gun armament supplanted by a Boulton-Paul turret mounting four .303 machine guns. It was tested operationally by the Fighter Interception Unit and No. 406 Squadron RCAF, but the turret installation drastically reduced performance and further development was abandoned.
Bristol 156 Beaufighter V R2274 at Boscombe Down in May 1941 with 4-gun forward-mounted turret 
Bristol 156 Beaufighter V R2274 at Boscombe Down in May 1941 with 4-gun forward-mounted turret