BL 6 inch Gun Mk 7
| BL 6-inch gun Mk VII | |
|---|---|
Aboard HMCS Prince David circa 1941
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| Type |
Naval gun Coastal defence gun Heavy field gun |
| Place of origin |  |
| Service history | |
| In service | 1901–72 (Fort Scratchley) 1915–18 (field use) |
| Wars | World War II |
| Production history | |
| Designer | Vickers |
| Designed | 1899 |
| Number built | 898 |
| Variants | Mk VII, Mk VIIv, Mk VIII, Mk XXIV |
| Specifications | |
| Weight | 16,875 lb (7,654 kg) (gun & breech) 25 tons (gun on field carriage) |
| Length | 279.228 inches |
| Barrel length | 269.5 in (6.85 m) (44.9 cal) |
| Crew | 9 |
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| Shell | Lyddite, HE, Shrapnel 100 lb (45 kg) |
| Calibre | 6 in (152 mm) |
| Breech | Welin interrupted screw |
| Recoil | 16.5 in (419 mm) |
| Rate of fire | 8 rpm |
| Muzzle velocity | 2,525 ft/s (770 m/s) (light charge) 2,775 ft/s (846 m/s) (heavy charge) |
| Maximum firing range | Field carriage Mk. II : 13,700 yd (12,500 m) Naval : 14,600 yd (13,400 m) (light charge); 15,800 yd (14,400 m) (heavy charge) |
| Filling weight |
Lyddite : 13 lb 5 oz (6.0 kg) Amatol : 8 lb 14 oz (4.0 kg) Shrapnel : 874 balls @ 27/lb |
The BL 6 inch gun Mark VII (and the related Mk VIII) was a British naval gun dating from 1899, which was mounted on a heavy traveling carriage in 1915 for British Army service to become one of the main heavy field guns in the First World War, and also served as one of the main coast defence guns throughout the British Empire until the 1950s.
The gun superseded the QF six-inch gun of the 1890s, a period during which the Royal Navy had evaluated QF technology (i.e. loading propellant charges in brass cartridge cases) for all classes of guns up to six inches to increase rates of fire. BL Mk VII returned to loading charges in silk bags after it was determined that with new single-action breech mechanisms a six-inch BL gun could be loaded, a vent tube inserted and fired as quickly as a QF six inch gun. Cordite charges in silk bags stored for a BL gun were also considered to represent a considerable saving in weight and magazine space compared to the bulky brass QF cartridge cases.
The gun was introduced on the Formidable-class battleships of 1898 (commissioned September 1901) and went on to equip many capital ships, cruisers, monitors, and smaller ships such as the Insect-class gunboat which served throughout World War II.
The Mk VIII in naval service was identical to the Mk VII, except that the breech opened to the left instead of to the right, for use as the left gun in twin turrets.
Guns were mounted in the following ships :
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