RML 12-inch 35-ton gun

RML 12-inch 35-ton guns were large rifled muzzle-loading guns used as primary armament on British battleships of the 1870s. They were the longer and more powerful of the two 12-inch British RML guns, the other being the 25-ton gun.

Design
This gun design originated in 1871 as an 11.6 inch gun firing a 700 lb projectile. Results were unsatisfactory, leading to the gun being bored out to 12 inch and firing a 706 lb shell.

Naval service
Guns were mounted on:
 * Devastation-class battleships of 1873

Note: The two 12-inch guns installed in HMS Thunderer (1872)'s forward turret were 12.5-inch 38-ton guns bored instead to 12 inches, and designated "12-inch 38-ton", as the necessary 12-inch 35-ton guns were not available. These 2 guns used the same charges and projectiles as the standard 12-inch 35-ton guns installed in Thunderer's aft turret which simplified the supply of ammunition. It was one of these "12-inch 38-ton" guns that was accidentally double-loaded and exploded on 2 January 1879.

Ammunition
When the gun was first introduced projectiles had several rows of "studs" which engaged with the gun's rifling to impart spin. Sometime after 1878, "attached gas-checks" were fitted to the bases of the studded shells, reducing wear on the guns and improving their range and accuracy. Subsequently, "automatic gas-checks" were developed which could rotate shells, allowing the deployment of a new range of studless ammunition. Thus, any particular gun potentially operated with a mix of studded and studless ammunition.

The gun's primary projectile was 706 lb "Palliser" armour-piercing shot, which were fired with a "battering charge" of 110 lb of "P" (gunpowder) for maximum velocity and hence penetrating power. Shrapnel and common (exploding) shells weighed 613 lb and were fired with a "full charge" of 85 lb "P" or 67 lb "R.L.G.".