| Is Artillery: | yes |
| Is Explosive: | yes |
| Is Uk: | yes |
| Is Ranged: | yes |
| BL 12-inch gun Mk X | |
| Origin: | United Kingdom |
| Wars: | World War I |
| Type: | Naval gun |
| Designer: | Vickers |
| Manufacturer: | Vickers |
| Unit Cost: | £9800 (1907)[1] |
| Service: | 1906 – 1923 |
| Caliber: | 12inches |
| Part Length: | 45feet bore (45 cal) |
| Breech: | Welin interrupted screw |
| Velocity: | 2700abbr=onNaNabbr=on[2] |
| Cartridge: | 850lb Lyddite, Armour-piercing, Shrapnel[3] |
| Max Range: | 22860m (75,000feet)[4] |
| Weight: | 57 tons barrel & breech[5] |
The BL 12 inch Gun Mark X[6] was a British 45-calibre naval gun which was mounted as primary armament on battleships and battlecruisers from 1906. It first appeared on .
The Mk X continued the trend of lengthening gun barrels as far as new construction methods would permit, in order to allow more cordite propellant to be used to attain higher projectile velocities. The Mk X increased the bore length from the Mk IX's 480to, increasing muzzle velocity from 2600ft/s2700ft/s.
Subsequent British attempts to further increase the power of 12-inch guns led to failure with the 50-calibre Mk XI and Mk XII guns; the Mk X was the last successful 12-inch British gun.
Mk X guns were mounted in the following ships which served throughout World War I:
From 1917 several Mk X guns were deployed ashore on the section of the Belgian coast still held by the Allies, near Nieuwpoort. They were part of the "Royal Naval Siege Guns" under the command of Admiral Sir Reginald Bacon, and were used for attacking German heavy gun batteries.