Mks I and II were several early proof guns that did not enter British service and Mk V was not made.

In the interim Elswick Ordnance continued to develop 8-inch guns in 40 calibre and 45-calibre lengths for export, mainly to Japan.

Mk III were low-powered 25-calibres guns mounted on : Mk IV were 30-calibres guns mounted in : Mk VI were 30 calibres guns mounted in : Mk VII were lighter 25-calibres low-powered guns firing a lighter 180-pound projectile used to equip Australian colonial navies and Australian and New Zealand coastal defences in response to expected Russian expansionism in the Pacific (The "Russian scares" of the 1880s).

In the event, no Russian invasion occurred and the guns were rarely if ever fired.

Four Mk VII coast defence guns were installed at Singapore in the 1880s-1890s : two atop Mount Serapong and two at Fort Tanjong Katong.