The again Ordnance BL 12 inch howitzer on truck, railway, a type of railway gun, 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

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

Mark V

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. 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.

Combat service

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.

Ammunition