| BL 15-inch Mark I naval gun | |
|---|---|
 As mounted on monitor HMS Terror, 1915 | |
| Type | Naval gun |
| Place of origin | United Kingdom |
| Service history | |
| In service | 1915–1959 |
| Used by | United Kingdom |
| Wars | World War I, World War II, Cold War |
| Production history | |
| Designed | 1912 |
| Produced | 1912–1918 |
| No. built | 186 |
| Specifications | |
| Mass | 100 long tons (100 t)[1] |
| Length | 650.4 inches (16.52 m)[1] |
| Barrel length | 630 inches (16 m) L42 |
| Shell | separate charges and shell |
| Shell weight | 1,938 pounds (879 kg) |
| Calibre | 15-inch (381.0 mm) |
| Recoil | 46 inches (1.2 m)[1] |
| Rate of fire | 2 rounds per minute |
| Muzzle velocity | 2,450–2,640 feet per second (750–800 m/s), with supercharge |
| Maximum firing range | 33,550 yards (30,680 m) (Mk XVIIB or Mk XXII streamlined shell @ 30°)[2] HMS Vanguard – 37,870 yards (34,630 m) @ 30°, with supercharges. |
The BL 15-inch Mark I succeeded the BL 13.5-inch Mk V naval gun. It was the first British 15-inch (380 mm) gun design and the most widely used and longest lasting of any British designs, and arguably the most successful heavy gun ever developed by the Royal Navy.[3] It was deployed on capital ships from 1915 until 1959 and was a key Royal Navy gun in both World Wars.