The Rolls-Royce 40 mm 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 A bomber is a military combat aircraft that utilizes air-to-ground weaponry to drop bombs, launch aerial torpedo, torpedoes, or deploy air-launched cruise missiles. There are two major classifications of bomber: strategic and tactical. Strateg ...

. It was envisaged as a suitable weapon for destroying tanks from the air. Experimental versions of the cannon were produced, including some with a

magazine A magazine is a periodical literature, periodical publication, print or digital, produced on a regular schedule, that contains any of a variety of subject-oriented textual and visual content (media), content forms. Magazines are generally fin ...

or belt feed for the ammunition. Examples were fitted to a Bristol Beaufighter and

Hawker Hurricane The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force (RAF). It was overshadowed in the public consciousness by ...

for testing, although never used in action. Development of the aircraft cannon to iron out problems came to an end in 1943 when the

Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force and civil aviation that existed from 1918 to 1964. It was under the political authority of the ...

lost interest in it and had started to favor the RP-3 rocket projectile as its preferred aircraft anti-tank weapon. The gun was designed by Italian engineer Spirito Mario Viale, Rolls Royce's chief armaments designer, at

Littleover Littleover is a village and suburb in the city of Derby, in Derbyshire, England, between Rose Hill, Derbyshire, Rose Hill, Normanton, Derbyshire, Normanton, Sunny Hill, Derbyshire, Sunny Hill and Mickleover, about southwest of Derby city centre ...

Derby Derby ( ) is a City status in the United Kingdom, city and Unitary authorities of England, unitary authority area on the River Derwent, Derbyshire, River Derwent in Derbyshire, England. Derbyshire is named after Derby, which was its original co ...

. The gun was tested on a small testing range at Sinfin near the Derby works without the usual precautions like red flags. Later trials were at an Army range at Manorbier of a gun mounted on a 30 cwt Morris truck (which by a fluke hit a target plane on its fourth shot) and at the Royal Navy's waterborne trials off Whale Island. Although the Rolls-Royce 40 mm cannon was never deployed in aircraft, with the

Fall of France The Battle of France (; 10 May – 25 June 1940), also known as the Western Campaign (), the French Campaign (, ) and the Fall of France, during the Second World War was the German invasion of the Low Countries (Belgium, Luxembourg and the Net ...

in 1940 the

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

found itself lacking armament in its coastal craft to respond to German

E-boat E-boat was the Western Allies' designation for the fast attack craft (German: ''Schnellboot'', or ''S-Boot'', meaning "fast boat"; plural ''Schnellboote'') of the Kriegsmarine of Nazi Germany during World War II; ''E-boat'' could refer to a pat ...

s. The

Admiralty Admiralty most often refers to: *Admiralty, Hong Kong * Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964 *The rank of admiral *Admiralty law Admiralty can also refer to: Buildings * Admiralty, Tra ...

became interested in the development of the 40 mm cannon as a weapon that could knock out an E-boat. The first sea trials of the cannon were undertaken in September 1940 and it entered service in 1941 after teething troubles were ironed out. The "Rolls gun" was deployed mainly on

motor gun boat The motor gunboat (MGB) was a small, high-speed British military vessel of the Second World War, which was armed with a mix of guns, in contrast to the physically similar motor torpedo boat (MTB), whose main offensive weapon were torpedoes. ...

s which were used in action in British waters and the

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

, where they were much used in the anti-aircraft role. Over 600 40 mm cannon were manufactured under sub-contract by

British United Shoe Machinery British United Shoe Machinery Ltd. (BUSM) was formed in England around the turn of the 20th century, as a subsidiary of the American United Shoe Machinery Corporation, United Shoe Machinery Company. For most of the 20th century, USM was the worl ...

(BUSM) in

Leicester Leicester ( ) is a city status in the United Kingdom, city, Unitary authorities of England, unitary authority area, and the county town of Leicestershire in the East Midlands of England. It is the largest city in the East Midlands with a popula ...

, since Rolls-Royce was forbidden by

Lord Beaverbrook William Maxwell Aitken, 1st Baron Beaverbrook (25 May 1879 – 9 June 1964), was a Canadian-British newspaper publisher and backstage politician who was an influential figure in British media and politics of the first half of the 20th century ...

, the

Minister of Aircraft Production The Minister of Aircraft Production was, from 1940 to 1945, the British government minister at the Ministry of Aircraft Production, one of the specialised supply ministries set up by the British Government during World War II. It was responsible ...

, to tie up resources on them.

Footnotes

Bibliography

* * {{refend Trial and research firearms of the United Kingdom Naval guns of the United Kingdom Aircraft artillery World War II artillery of the United Kingdom Rolls-Royce Weapons and ammunition introduced in 1940

See also

Footnotes

Bibliography