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Ordnance BL 12 inch Howitzer Mk I, III, V on truck, railway
Mk. I "Hilda" in action, Ypres, 7 November 1917
Type Railway howitzer
Place of origin  United Kingdom
Service history
In service 1916 - 1940
Used by  United Kingdom
Wars First World War
Production history
Designer Elswick Ordnance Company
Manufacturer Elswick Ordnance Company
Number built 81
Variants Mk I, III, V[1]
Barrel length Mk I: 12 ft (3.7 m)
Mk III & V: 17 ft 3 in (5.26 m)[2]

Shell HE; 750 lb (340 kg)
Calibre 12 inch (305 mm)
Elevation Mk I & III: 40° - 65°
Mk V: 20° - 65°
Traverse Mk I & III: 20° L & R
Mk V: 120° L & R[2]
Muzzle velocity Mk I: 1,175 ft/s (358 m/s)
Mk III & V: 1,468 ft/s (447 m/s)[2]
Effective range Mk I: 11,132 yd (10,179 m)
Mk III: 15,000 yd (14,000 m)
Mk V: 14,350 yd (13,120 m)
Filling weight 83lb 3oz (37.96 kg) Amatol

The Ordnance BL 12 inch howitzer on truck, railway was developed following the success of the 9.2 inch siege howitzer. It was similar but unrelated to the 12 inch siege howitzers Mk II and IV.

Design and development

Mark I

Mk I was introduced from March 1916. It is identified by its short barrel and recuperator above the barrel.

Mark III

Mk III at Wareham, Dorset, 26 February 1941

The longer-barrelled Mk III soon followed, with a heavier breech to balance the gun. It retained the recuperator above the barrel.

Mark V

One Mk V (foreground) and two Mk IIIs, Catterick UK, 12 December 1940

Mk V, dating from July 1917, moved the recoil buffer and recuperator into a single housing below the barrel, which was common for all new British artillery developed during World War I. It also had a lighter breech with the gun balanced by the redesigned recoil system and altered gun positioning on the cradle.[3] Mk V also relocated the loading platform from the railway wagon to the revolving gun mounting, which now allowed 120° of traverse, and by overhanging the opposite side provided crew access when the gun fired to the side (90° traverse) and also helped to balance it.[3]

Combat service

Mk V in action at Soissons, France, 19 May 1918

All 3 versions served on the Western Front in World War I, usually in 2-gun batteries, operated by the Royal Garrison Artillery.

Mk III and MK V were deployed for the home defence of Great Britain in World War II.


See also


  1. Mk I = Mark 1, Mk III = Mark 3, Mk V = Mark 5. Britain used Roman numerals to denote Marks (i.e. models) of ordnance until after World War II. This article covers the first, third and fifth models of British 12-inch howitzers.
  2. 2.0 2.1 2.2 Hogg & Thurston 1972, page 179, 183, 187
  3. 3.0 3.1 Hogg & Thurston 1972, page 186


Further reading

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