During the 1870s the Admiralty had been developing a new naval gun with armour piercing capabilities, the design of which was finally perfected in 1876. A Rifled Muzzle Loader or R.M.L. it weighed 81 tons, was 26 feet 9 inches long and fired a 1,700 pound shell just under 7 miles. Each gun cost £10,000 and each round of ammunition over £26. It was first regarded as purely a naval weapon, but in 1877 the Admiralty decided that something larger than the existing guns was needed to protect Dover, and the idea of a turret containing two of these weapons at the end of the Admiralty Pier was born. The pier head was modified, at a cost of £60,000, to house the magazine with an engine room below and the turret above. The turret, 37 feet in diameter and weighing, with the guns in their mountings, 895 tons, cost £90,000. The engine room in the heart of the pier head and below the high water mark, housed two steam engines to rotate the turret, one to work the ammunition hoists, loading gear and to run the guns in and out, one to operate a dynamo giving 33 volts for lighting and a steam pump to provide water under pressure for hosing out the guns between rounds.The guns were brought from Woolwich to Dover by ship and were installed in the turret using block and tackle. The muscle power was provided by no less than 1,000 men of the Dover garrison stretching the length of the pier.In 1883 the guns were tested amid local fears of damage to the cliffs and windows and roof tiles in the town. Crowds gathered on the Sea Front to watch the effects of the firing but the only damage was to the lighthouse at the end of the Admiralty Pier where three small panes of glass were broken. More tests were carried out early in 1886 and the turret handed over on 21st April. There is no record of the guns having ever been fired again and in 1902 the Dover Turret was declared obsolete. In 1898 it had been suggested that the turret guns should be replaced with 9.2 inch breech loaders but this was never done. The guns were run in for the last time greased and depressed to the loading position and left. The steam engines and ammunition hoists have been removed as has the gear for running the guns in and out but the guns themselves still remain inside the turret.