page_title: Rolls-Royce 40mm Cannon
hierarchical_section_title: Rolls-Royce 40mm Cannon
caption_attribution_description: English: Rolls-Royce type BH 40mm Aircraft Cannon (1942) on display at the Silk Mill Museum, Derby, in 2010. May not now be on display. From the display captions: "As early as 1938 Hives [Ernest Hives, General Works Manager and a director of Rolls-Royce] was concerned about the lack of British made guns for aircraft. As a stimulus to the arms manufacturers a small armaments section was set up at Rolls-Royce in Derby. This developed a 40mm quick firing cannon." "Intended for tank busting aircraft such as the Hurricane IID, a small number were fitted to these aircraft in 1942, but never saw action due to a change in tactics and the development of rockets." "After the fall of France the Admiralty expressed an interest in using the gun on their motor boats. Over 600 naval versions of the cannon were built at the British United Shoe Machinery Company in Leicester." "The gun on display is a Mk II, model BH with a 12 round magazine intended for Hurricane IID tank busting aircraft. It is on display from the RAF Museum, Hendon."
context_page_description: The Rolls-Royce 40mm Cannon was a project first proposed in late 1938 to produce a cannon for mounting in aircraft which could cause sufficient damage to bring down a large bomber. It was also envisioned to be a suitable weapon for destroying tanks from the air. Experimental versions of the cannon were produced including some with a magazine or belt feed for the ammunition. Examples were fitted to a Beaufighter and Hurricane for testing, although never used in action. Continued development of the aircraft cannon to iron out problems came to an end in 1943 when the Air Ministry lost interest in it and had started to favor the rocket projectile as its aircraft anti-tank weapon of choice.
  Although the Rolls-Royce 40mm cannon was never deployed in aircraft, with the Fall of France in 1940 the Royal Navy found itself with very little effective armament in its coastal craft to respond to German E-boats. The Admiralty became interested in the development of the 40mm Cannon as a weapon that could knock out an E-boat. The first sea trials of the cannon were successfully undertaken in September 1940 and it entered service in 1941 after teething troubles were ironed out.
context_section_description: The Rolls-Royce 40mm Cannon was a project first proposed in late 1938 to produce a cannon for mounting in aircraft which could cause sufficient damage to bring down a large bomber. It was also envisioned to be a suitable weapon for destroying tanks from the air. Experimental versions of the cannon were produced including some with a magazine or belt feed for the ammunition. Examples were fitted to a Beaufighter and Hurricane for testing, although never used in action. Continued development of the aircraft cannon to iron out problems came to an end in 1943 when the Air Ministry lost interest in it and had started to favor the rocket projectile as its aircraft anti-tank weapon of choice.
  Although the Rolls-Royce 40mm cannon was never deployed in aircraft, with the Fall of France in 1940 the Royal Navy found itself with very little effective armament in its coastal craft to respond to German E-boats. The Admiralty became interested in the development of the 40mm Cannon as a weapon that could knock out an E-boat. The first sea trials of the cannon were successfully undertaken in September 1940 and it entered service in 1941 after teething troubles were ironed out. The "Rolls gun" was deployed mainly on motor gunboats which were used in action in British waters and the Mediterranean, where they were much used in the anti-aircraft role. Over 600 40mm cannon were manufactured under sub-contract by British United Shoe Machinery (BUSM) in Leicester, since Rolls-Royce was forbidden by Lord Beaverbrook, who was then Minister of Aircraft Production, to tie down resources on them.
caption: Rolls-Royce type BH 40mm Aircraft Cannon (1942) on display at the Silk Mill Museum, Derby, in 2010.
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