BL 7.5-inch Mk II – V naval gun

The BL 7.5-inch guns Mk II - Mk V were a variety of 50-calibre naval guns used by Britain in World War I. They all had similar performance and fired the same shells.

Mark II
Mark II guns were originally developed to suit India's coast defence requirements. During World War I several reserve guns made for India but still in the UK were employed as coast defence guns in the UK. They were scrapped or sent to India soon after the war.

Marks II*, II**, V
These were built and employed specifically as naval guns and were mounted as secondary armament as a heavier alternative to 6-inch guns, on the following ships : 
 * Warrior-subclass armoured cruisers HMS Warrior, HMS Cochrane, HMS Achilles and HMS Natal laid down 1903–04, commissioned 1906–07
 * Minotaur-class armoured cruisers laid down 1905, commissioned 1908–09

Mark III
Mark III guns were built by Elswick Ordnance to arm the battleship Constitución they were building for Chile. Britain acquired them by default when she bought Constitución in 1903 to avoid the risk of the ship being acquired by Russia. Constitución became HMS Swiftsure in British service.

Swiftsure was decommissioned in 1917 and her guns were used for coast defence in Britain, as siege guns on the Belgian coast near Nieuport for attacking German batteries, and on M15-class monitors. 

Mark IV
Mark IV guns were made by Vickers for the battleship Libertad they were building for Chile. Britain acquired them by default in 1903 when she bought Libertad together with Constitución. Libertad became HMS Triumph (1903) in British service.

Surviving examples

 * Two Mk II coast-defence guns made by E.O.C. in 1905 and R.G.F. in 1906, on Elephanta Island, Mumbai, India. Photographs on Flickr