Ordnance RML 12-inch 35-ton gun
An interior view of one of the two main battery turrets aboard the British battleship HMS Devastation, showing a rear view of the turret's two 12-inch (305 mm) 35-ton rifled muzzle-loaders. These guns were replaced in 1891 by 10-inch (254 mm) breech-loading rifles.
Type	Naval gun
Service history
In service	1873–1909
Used by	Royal Navy
Production history
Designed	1871
Manufacturer	Royal Arsenal
Unit cost	£2,154[1]
No. built	15[2]
Specifications
Mass	35 long tons (36,000 kg)
Barrel length	162.5 inches (4.13 m) (bore + chamber)[3]
Shell	706 pounds 12 ounces (320.6 kg) (Palliser) 613 pounds (278.1 kg) (Common & Shrapnel)
Calibre	12-inch (304.8 mm)
Muzzle velocity	1,390 feet per second (420 m/s)[4]

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 (295 mm) gun firing a 700-pound (317.5 kg) projectile. Results were unsatisfactory, leading to the gun being bored out to 12 inches (305 mm) and firing a 706-pound-12-ounce (320.6 kg) shell.^[2]

Naval service

Guns were mounted on:

• Devastation-class battleships of 1873

Note: The two 12-inch guns installed in HMS Thunderer'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.^[5] It was one of these "12-inch 38-ton" guns that was accidentally double-loaded and exploded on 2 January 1879.

Ammunition

• 
  Studded Palliser, Common and Shrapnel projectiles
• 
  Studless Palliser, Common and Shrapnel projectiles

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 (320 kg) "Palliser" armour-piercing shot, which were fired with a "battering charge" of 110 lb (50 kg) of "P" (gunpowder) for maximum velocity and hence penetrating power. Shrapnel and common (exploding) shells weighed 613 lb (278 kg) and were fired with a "full charge" of 85 lb (39 kg) "P" or 67 lb (30 kg) "R.L.G.".^[6]