6inchguns

The 6-inch Mk-7 could be considered the backbone of Coastal Defences built around the British Empire. Brought into service in 1898. The 6-inch gun weighs roughly 7.4 tonnes (excluding carriage). A compliment of 12 men was required to operate each gun which was fired either by percussion or electric contact. A fused shell was rammed through the breach until the driving band was hard against the front of the chamber; the cartridge was then inserted and the breeched closed. The projectiles used were either armour-piercing shells or Lyddite common shell. The firing action caused the gun to recoil 0.5 metres before returning to its original loading position. The rate of fire for these guns was six rounds a minute.

Two of these guns were mounted at Fort Dorset in 1910 (you can see a picture of the guns in the site article). A further two were emplaced at Fort Opau during the Second World War.
Below is a rough drawing of how the gun would have looked like sitting in its pit. (CP-II mount)

This weapon was originally developed for Chile for the battleships of the Admirante Latorre Class then building in British shipyards. Twelve were made by the Elswick Ordnance Company between 1916-22. However when it came for the Chilean Government to take delivery, they declined to do so due to the state of their economy. The guns were then incorporated into British service as the MkXXI, but put into store. The MkXXI was declared obsolescent on 26 April 1927, along with the MkVII. This of course does not mean they were obsolete, just that they had been replaced in production by newer marks, namely the MkXXIV. The MkXXI, and long with the MkVII, XXIII and XXIV were all declared obsolete on 18 August 1959. Two were installed at Palmer Head in the 1930s, with a third one installed during the Second World War. Below is a rough drawing of how the gun would have looked like sitting in its pit (without overhead cover).