BL 8-inch Mk I – VII naval gun

The BL 8 inch guns Mark I to Mark VII[note 2] were the first generations of British rifled breechloaders of medium-heavy calibre. They were initially designed for gunpowder propellants and were of both 25.5 and 30 calibres lengths.

Ordnance BL 8 inch gun Mks I - VII
TypeNaval gun
Coast defence gun
Place of originUnited Kingdom
Service history
In service1884 - 190?
Used by United Kingdom
Colonial navies of Australia
 New Zealand
 Singapore
Production history
DesignerMk I, VI : RGF
Mk VII : EOC
ManufacturerMk I, III, IV : RGF
Mk III, IV, VI, VII EOC
Unit cost£6,015[1]
VariantsMks III, IV, VI, VII, VIIA
Specifications
MassMk III & VI : 14 tons
Mk IV : 15 tons
Mk VII : 12 tons
Mk VIIA : 13 tons barrel & breech[2]
Barrel lengthMk III : 201 inches (5,105 mm)
Mk VII : 204 inches (5,182 mm)
Mk IV & VI : 237 inches (6,020 mm) bore[2]
ShellMks III, IV, VI : 210 pounds (95.25 kg)
Mk VII : 180 pounds (81.65 kg)[note 1]
Calibre8-inch (203.2 mm)
Muzzle velocityMk III : 1,953 feet per second (595 m/s)[3]
Mk IV & VI : 2,150 feet per second (655 m/s)[4]
Mk VII : 2,000 feet per second (610 m/s)[5][6]
Maximum firing range8,000 yards (7,300 m)[2][7]

History

Mks I and II were several early proof guns that did not enter British service and Mk V was not made. Limited numbers of 25.5 and 30 calibres guns were produced.

By 1885 the Royal Navy abandoned the 8-inch gun in favour of the 9.2 inch and later the 7.5 inch gun for cruisers, until 1923 when the restrictions of the Washington Naval Treaty led Britain to develop the Mk VIII 8-inch gun in order to arm heavy cruisers with the largest gun allowed by the Treaty.

In the interim Elswick Ordnance continued to develop 8-inch guns in 40 calibre and 45-calibre lengths for export, mainly to Japan.

Mark III

Mk III were low-powered 25-calibres guns mounted on :

Mark IV

Mk IV were 30-calibres guns mounted in :

Mark VI

Mk VI were 30 calibres guns mounted in :

Mark VII

Mk VII were lighter 25-calibres low-powered guns firing a lighter 180-pound projectile used to equip Australian colonial navies and Australian and New Zealand coastal defences in response to expected Russian expansionism in the Pacific (The "Russian scares" of the 1880s).

As mounted in bow of Gayundah, 1903

Mk VII guns armed the following Australian colonial gun vessels :

Coast defence gun
At Fort Queenscliff, Victoria, Australia

Mk VII guns were installed on disappearing mountings in Australia and New Zealand as coast-defence guns during the "Russian scares" of the 1880s. In the event, no Russian invasion occurred and the guns were rarely if ever fired.

Four Mk VII coast defence guns were installed at Singapore in the 1880s-1890s : two atop Mount Serapong and two at Fort Tanjong Katong.[8]

Ammunition
  • 210 pound Mk I common shell

Surviving examples

See also

Notes
  1. Different types of shell had different weights : figures are for the gun's heaviest shell. Hence for the Mk VII gun the Victorian Navy Manual of 1895 quotes Common 168 lb, Segment 177 lb, Palliser, Case & Shrapnel 180 lb
  2. Mark I to Mark VII = Mark 1 to Mark 7. Britain used Roman numerals to denote marks (models) of ordnance until after World War II. Hence these were the first 7 models of BL 8-inch naval gun.

References
  1. Unit price for 10 Mk VII guns on hydro-pneumatic carriages, with 50 rounds per gun, delivered in London, as purchased by New Zealand in 1885. 1885 New Zealand Harbour defences (Table showing amount required for) Laid on the Table by the Hon. Mr Ballance, with the Leave of the House. Archived 15 October 2008 at the Wayback Machine
  2. Text Book of Gunnery 1902, Table XII Page 336
  3. Mk III : 1953 ft/s firing 210-pound projectile using 104 lb Prismatic Brown powder or 28 lb 12 oz cordite Mk I size 20. Text Book of Gunnery 1902.
  4. Mks IV & VI : 2150 ft/s firing 210-pound projectile using 118 lb Prismatic brown powder or 32 lb 10 oz cordite Mk I size 20. Text Book of Gunnery 1902.
  5. Mk VII : 2,000 ft/s firing a 180 lb projectile, with 90 lb black prism powder (gunpowder); or 22 lb cordite MK I propellant size 20. Text Book of Gunnery, 1902
  6. Mk VII : Victorian Navy Manuals 1887 and 1895 quote 100 lb Black powder for "battering charge" and 90 lb for regular charge. Muzzle Velocity of 2027 ft/s is quoted with 180 lb projectile and 90 lb charge in the Victorian Navy Manual of 1895
  7. 12000 yards is quoted for Mk VII gun in the Victorian Navy Manual of 1895
  8. "Fort Siloso. The Gun Museum. 8-inch BL gun". Archived from the original on 11 January 2010. Retrieved 15 July 2010.
  9. Northcote's cannons - defending the neighbourhood Archived 2 July 2018 at the Wayback Machine Darebin Heritage

Bibliography
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