BL 12 inch Mk XI – XII naval gun

The BL 12 inch Gun Mark XI and Mark XII were British 50-calibres naval guns that were mounted as primary armament on dreadnought battleships from 1910.

History
Mk XI had a longer (50 calibres, 600 inches) barrel than the previous Mk X gun (45 calibres), and was an attempt to increase the muzzle velocity, and hence armour-piercing capability and range, of a 12 inch gun. The muzzle velocity increased from 2700 ft/s to 2825 ft/s but problems such as bore erosion, which led to short barrel life, and poor accuracy due to inconsistent cordite propellant burning, meant the gun was not entirely satisfactory. The subsequent Mk XII gun suffered from the same problems.

Instead of attempting to improve the 12-inch gun, the British developed the 13.5-inch Mk V gun of 45-calibres, as it could achieve greater range at lower muzzle velocities due to its larger shell.

Mk XI guns were mounted in the following ships :
 * St. Vincent-class battleships laid down 1907, commissioned 1910
 * HMS Neptune laid down 1909, commissioned 1911

Mk XII guns were mounted in the following ships :
 * Colossus-class battleships laid down 1909, commissioned 1911

Weapons of comparable role, performance and era

 * Obukhovskii 12"/52 Pattern 1907 gun Russian equivalent
 * 30.5 cm SK L/50 gun German equivalent