|West Spring Gun|
|Place of origin||United Kingdom|
|Used by||United Kingdom|
|Wars||World War I|
|Designer||Captain Allen West|
|Manufacturer||Reason Manufacturing Company|
|Mass||284 lb (129 kg)|
|Length||71.5 in (182 cm)|
|Width||18.5 in (47 cm)|
|Height||88 in (220 cm)|
|Effective firing range||240 yd (220 m)|
It consisted of a metal frame supporting a throwing arm powered by 24 metal springs. It was invented by Captain Allen West in 1915 and manufactured by the Reason Manufacturing Company of Brighton, which was granted a patent for the device on 19 October of that year. Although called a catapult, it was a hybrid of a ballista and a trebuchet. It required a crew of five - three to compress the springs, one to load the bomb, and one to fire as soon as the fuse was lit or the grenade pin was pulled.
In tests, it could throw Mills bomb about 240 yd (220 m) or a 7 lb (3.2 kg) projectile about 80 yd (73 m) with a flight time of 6 or 7 seconds. In the field it generally threw a Jam Tin Grenade, No. 15 Ball grenade, No. 21 "Spherical" grenade or No. 28 chemical grenade, equipped with a slightly longer fuse (typically 9 seconds) to ensure to reach the enemy trench before exploding. It was used in combat by, amongst others, the 50th (Northumbrian) Division and the 1st Canadian Division in the Second Battle of Ypres and by Australian forces in the Gallipoli Campaign. It was generally considered to be large and cumbersome and "generally more unwieldy" than the Leach Trench Catapult. Many operators, including Captain West himself, lost fingers in the mechanism. The throw could also be unpredictable, with the bomb sometimes landing near the thrower.
- Gary Sheffield (2007). War on the Western Front: In the Trenches of World War I. Osprey Publishing. p. 201. ISBN 978-1846032103.
- Anthony Saunders (1999). Weapons of the Trench War: 1914-1918. Sutton. p. 65. ISBN 978-0750918183.
- Clifford Almon Wells (1917). From Montreal to Vimy Ridge and beyond: the correspondence of Lieut. Clifford Almon Wells, B.A., of the 8th battalion, Canadians, B.e.f., November, 1915-April, 1917. George H. Doran company. p. 87.
- The Royal Engineers Journal. 39: 79. 1925. Missing or empty
- Kenneth Radley (2006). We lead, others follow: First Canadian Division, 1914-1918. Vanwell. p. 120. ISBN 978-1551251004.
- "Grenade, West Spring Gun, No 21 R Type". Imperial War Museum.
- Hugh Chisholm (1922). The Encyclopædia Britannica: The New Volumes, Constituting, in Combination with the Twenty-nine Volumes of the Eleventh Edition, the Twelfth Edition of that Work, and Also Supplying a New, Distinctive, and Independent Library of Reference Dealing with Events and Developments of the Period 1910 to 1921 Inclusive, Volume 1. Encyclopædia Britannica Company Limited. p. 470.
- No 21 R Type grenade for the West Spring Gun at the Imperial War Museum.
- West Spring Gun (missing its launch arm) at the Australian War Memorial.