Mk III : 24 tons The BL 9.2-inch Mk I–VII guns[note 2] were a family of early British heavy breechloading naval and coast defence guns in service from 1881 to the end of World War I.

When surplus BL 9.2 inch Mk IV and Mk VI guns became available in the 1890s they were likewise adapted to high-angle carriages, with their obsolete 3-motion breech mechanisms replaced by modern continuous-motion patterns to allow faster loading.

[5] The elevation of up to 45° meant that the shell was at risk of slipping back after being rammed forward as only the copper driving band held the shell in place in a BL gun, and they had not been designed to operate at such high angles.

The solution adopted was to develop a special high-angle reduced-charge cartridge with a hollow up the centre, through which the gunner inserted a 1+1⁄4-inch-diameter (32 mm) stick about 40 inches long made of beech wood, to prevent the projectile from slipping back before firing.

[8] In the late 1880s and early 1890s the Australian colonies between them ordered 10 barrels and nine carriages for BL 9.2 inch Mk VI 'counter bombardment' disappearing guns:[9]