Military Wiki
Ordnance QF 1½ pdr Mk III
Type Autocannon
Place of origin United Kingdom
Service history
In service 1918 - 1940s
Used by  United Kingdom
Production history
Designer Coventry Ordnance Works
Manufacturer Coventry Ordnance Works
Variants Mk III, Mk IV
Weight 200 pounds (91 kg) for cradle, gun & breech[1]
Length 91.8 inches (2.33 m) total
Barrel length bore of 75 inches (1.9 m)[1]

Shell 37x190R HE 1 lb 7 oz (0.65 kg)
Calibre 37 mm (1.457 in)
Barrels 1
Action automatic, gas operated
Muzzle velocity 1,950 ft/s[1]

The COW 37 mm gun was a British automatic cannon that was developed as a heavy-calibre aircraft weapon. It was trialled in several installations and specified for the Westland C.O.W. Gun Fighter. However they did not yield results and the weapon did not enter general service.

Design and development

Coventry Ordnance Works had been set up in 1905 by a consortium of British shipbuilding firms (John Brown, Cammell Laird and Fairfield) in order to compete with the duopoly of Vickers and Armstrong-Whitworth in producing naval guns. Besides the larger naval gun, COW worked at the smaller end on anti-aircraft guns. There was a demand for a gun that could be mounted on an aircraft. Their first attempt at an automatic gun was a "1-pounder" (the nominal weight of the shell) from a rimless 37x94 cartridge. This developed into a 1½-pounder using a longer 37x190 cartridge in a five-round clip. The gun was ready to produce only as the First World War came to an end and was only in service briefly fitted to a pair of Airco DH4s.[2]

Post war it was tried in a number of different aircraft, mostly flying boats such as the Blackburn Perth, where it was seen as being effective against small vessels but also in fighters. The Air Ministry specifically requested designs that could use the weapon, such as the Westland C.O.W. Gun Fighter and the Vickers Type 161.

After Vickers acquired the Coventry Ordnance Works, the COW 37 mm was used as for the development of the 40 mm Vickers S gun which was used by Hawker Hurricanes as an anti-tank weapon.

In the Second World War, COW guns were used as the armament for the Mk III version of the Armadillo armoured fighting vehicle; the COW gun with its shield on the rear part of the flatbed.[3] The vehicle was used by the RAF for airfield defence and later the Home Guard.


File:Bedford OYD Armadillo MK III.jpg

Bedford Armadillo Mk III Gun truck fitted with a COW 37 mm gun

Specification 4/24
Specification F9/27
Flying boats

See also



  • I.V. Hogg & L.F. Thurston, British Artillery Weapons & Ammunition 1914-1918. London: Ian Allan, 1972
  • Flight JUNE 28, 1934

External links

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