The 100 tonners (together with their brothers, the 80-ton guns at Dover) were the first of the new weapons of the technological era – the only guns in the British Army which were completely operated by machinery and could not be worked by hand. As a result, they gave many headaches. A steam engine, which took about four minutes to build up sufficient head of steam to operate the gun, charged accumulators which fired the weapon electrically, one round every four minutes. The projectiles and charges were moved on an underground railway from magazines to the ammunition hoists where they were automatically lifted to the gun barrel and rammed into the muzzle b y a steam-operated ram. After firing, automatic water jets swilled out of the gun.
It was a complicated process backed by a gun crew of 35 men. No wonder it occasionally went wrong. Once during firing practice, a cartridge failed to detonate and its shell remained in the barrel – a nasty situation especially in view of the fact that one of the guns of the Italian battleship Duilio had recently blown up. A small, thin trumpeter was asked to volunteer to retrieve the shell from the British gun. Some idea of the size of the bore – a calibre of 17½ inches – can be gained from the fact that it was possible to lower this man, head first, down the barrel, clutching a stout rope in his hands. This he secured to an eye conveniently provided on the tip of the shell, and first he was drawn out, then the unexploded shell. He was promoted to the rank of bombardier on the spot.’ This latter event took place in 1902 during the official visit to the Rock by the Inspector-General of Artillery, with the gun then prepared to fire five rounds at full charge.
Link to 100-ton gun