BL 12 inch Mk XI – XII naval gun

BL 12 inch gun Mk XI, Mk XII
Aft Mk XII guns of HMS Hercules
Type	Naval gun
Place of origin	United Kingdom
Service history
In service	1910–1920
Wars	World War I
Production history
Designer	Vickers
Manufacturer	Vickers Armstrong Whitworth Coventry Ordnance Works William Beardmore and Company
Specifications
Barrel length	50 ft (15.24 m) bore (50 calibers)
Shell	850 lb (385.6 kg) Lyddite, Armour-piercing, Shrapnel
Calibre	12 inches (304.8 mm)
Muzzle velocity	2,825 ft/s (861 m/s)
Maximum firing range	19,380 m (21,190 yd)

Vickers Armstrong Whitworth Coventry Ordnance Works

The BL 12 inch Gun Mark XI and Mark XII were British breech loading (BL) naval guns of 50-calibres length mounted as primary armament on dreadnought battleships from 1910.

In an effort to increase the armour-piercing capability and range of a 12 inch gun, the 50 calibres/600 inches Mk XI's barrel was 5 calibres/60 inches longer than the previous Mk X gun's 45 calibres. As a result, muzzle velocity increased from 2,700 feet per second (820 m/s) to 2,825 feet per second (861 m/s), but bore erosion, which led to short barrel life, and poor accuracy due to inconsistent cordite propellant burning, hampered the gun. The Mk XII derived from it suffered from the same problems.

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

Mk XI guns were mounted on:

Mk XII guns were mounted on: