 The armament of the Admiralty Pier Fort was to be two 12-inch muzzle-loading rifled guns of 25 tons as these guns were the most powerful available at the time.In 1877 the Defence Committee noted that more powerful guns of 80 tons had been developed and they recommended that a turret be fitted on the Admiralty Pier Fort for two 80-ton guns.The Superintendent of the Royal Gun Factory had been asked for designs for a powerful gun for capable of penetrating 20 inches of iron at a range of 1,000 yards and it was these guns that were eventually used as armament for the turret on the Admiralty Pier Fort.