BL 8-inch Mk I – VII naval gun

Ordnance BL 8 inch gun Mks I - VII
Ordnance BL 8 inch gun Mks I - VII
	Mk VII on disappearing carriage at North Head, Devonport, New Zealand
Type	Naval gun; Coast defence gun
Place of origin	United Kingdom
Service history
In service	1884 - 190?
Used by	United Kingdom; Colonial navies of Australia; New Zealand; Singapore
Production history
Designer	Mk I, VI : RGF; Mk VII : EOC
Manufacturer	Mk I, III, IV : RGF; Mk III, IV, VI, VII EOC
Unit cost	£6,015
Variants	Mks III, IV, VI, VII, VIIA
Specifications
Mass	Mk III & VI : 14 tons; Mk IV : 15 tons; Mk VII : 12 tons; Mk VIIA : 13 tons barrel & breech
Barrel length	Mk III : 201 inches (5,105 mm); Mk VII : 204 inches (5,182 mm); Mk IV & VI : 237 inches (6,020 mm) bore
Shell	Mks III, IV, VI : 210 pounds (95.25 kg); Mk VII : 180 pounds (81.65 kg)
Calibre	8-inch (203.2 mm)
Muzzle velocity	Mk III : 1,953 feet per second (595 m/s); Mk IV & VI : 2,150 feet per second (655 m/s); Mk VII : 2,000 feet per second (610 m/s)
Maximum firing range	8,000 yards (7,300 m)

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.

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 :

HMS Bellerophon as re-gunned in 1885

Mark IV

Mk IV were 30-calibres guns mounted in :

Mersey-class cruisers of 1885

Mark VI

Mk VI were 30 calibres guns mounted in :

Indian monitors Abyssinia and Magdala as re-gunned in 1892

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).

Naval service

Mk VII guns armed the following Australian colonial gun vessels :

Coast defence gun

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

Mk VII at North Head, Devonport, New Zealand
Mk VII at summit of Mount Victoria, Auckland, New Zealand
An unrestored Mk VII disappearing gun at Fort Jervois, Ripapa Island, New Zealand
Mk VII at Fort Siloso, Sentosa Island, Singapore See also Photograph at Flickr
Mk VII at Royal Artillery Museum, Woolwich, London
A Mk VII gun from 1885 on hydro-pneumatic mounting at Fort Queenscliff, Victoria, Australia
A pair of Mk VII guns at High Street in Westgarth / Northcote, Victoria, Australia ^[9]
A pair of Mk VII guns at Kangaroo Battery, Rosny, Tasmania, Australia (INCORRECT, these guns are 8in RML, not BL)

Notes

^ 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
^ 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

^ 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
^ ^a ^b ^c Text Book of Gunnery 1902, Table XII Page 336
^ 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.
^ 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.
^ 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
^ 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
^ 12000 yards is quoted for Mk VII gun in the Victorian Navy Manual of 1895
^ "Fort Siloso. The Gun Museum. 8-inch BL gun". Archived from the original on 11 January 2010. Retrieved 15 July 2010.
^ Northcote's cannons - defending the neighbourhood Archived 2 July 2018 at the Wayback Machine Darebin Heritage

Bibliography

External links

Handbook for the 8-inch b.l. gun marks VII and VIIa Land service 1899 From State Library of Victoria.
Instructions for 8 inch Rifled Breech Loading Armstrong Gun and Hydro-Pneumatic Disappearing Carriage Describes Mk VII gun. From Australian National Archives
Instructions for 8 inch Rifled Breech Loading Armstrong Gun and Naval Carriage and Slide Describes Mk VII gun. From Australian National Archives

[3] 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

[9] 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.

[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

[Gunnery1902-2] Text Book of Gunnery 1902, Table XII Page 336

[4] 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.

[5] 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.

[6] 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

[7] 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

[8] 12000 yards is quoted for Mk VII gun in the Victorian Navy Manual of 1895

[10] "Fort Siloso. The Gun Museum. 8-inch BL gun". Archived from the original on 11 January 2010. Retrieved 15 July 2010.

[11] Northcote's cannons - defending the neighbourhood Archived 2 July 2018 at the Wayback Machine Darebin Heritage

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