BL 8 inch Mk I – VII naval gun

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Ordnance BL 8 inch gun Mks I - VII

BL 8 inch Mk VII disappearing gun Devonport NZ November 2008.jpg

Type Naval gun
Coast defence gun
Place of origin United Kingdom
Service history
In service 1884 - 190?
Used byFlag of the United Kingdom.svg  United Kingdom
Colonial navies of Australia
Flag of New Zealand.svg  New Zealand
Flag of Singapore.svg  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 [1]
Variants Mks III, IV, VI, VII, VIIA
Specifications
Weight Mk III & VI : 14 tons
Mk IV : 15 tons
Mk VII : 12 tons
Mk VIIA : 13 tons barrel & breech [2]
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 [2]
Shell Mks III, IV, VI : 210 pounds (95.25 kg)
Mk VII : 180 pounds (81.65 kg) [note 1]
Calibre 8-inch (203.2 mm)
Muzzle velocity Mk 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 range 8,000 yards (7,300 m) [2] [7]

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.

Contents

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.

Washington Naval Treaty treaty among the major nations that had won World War I

The Washington Naval Treaty, also known as the Five-Power Treaty, the Four-Power Treaty, and the Nine-Power Treaty, was a treaty signed during 1922 among the major nations that had won World War I, which agreed to prevent an arms race by limiting naval construction. It was negotiated at the Washington Naval Conference, held in Washington, D.C., from November 1921 to February 1922, and it was signed by the governments of the United Kingdom, the United States, France, Italy, and Japan. It limited the construction of battleships, battlecruisers and aircraft carriers by the signatories. The numbers of other categories of warships, including cruisers, destroyers and submarines, were not limited by the treaty, but those ships were limited to 10,000 tons displacement each.

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 :

HMS <i>Abyssinia</i> (1870) coast defence monitor

HMS Abyssinia was a breastwork monitor ordered, designed and built by J & W Dudgeon specifically for the Bombay Marine for the defence of the harbour at Bombay.

HMS <i>Magdala</i> (1870)

HMS Magdala was a Cerberus-class breastwork monitor of the Royal Navy, built specifically to serve as a coastal defence ship for the harbour of Bombay in the late 1860s. She was ordered by the India Office for the Bombay Marine. The original specifications were thought to be too expensive and a cheaper design was ordered. While limited to harbour defence duties, the breastwork monitors were described by Admiral George Alexander Ballard as being like "full-armoured knights riding on donkeys, easy to avoid but bad to close with." Aside from gunnery practice Magdala remained in Bombay Harbour for her entire career. The ship was sold for scrap in 1903.

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).

Colonial navies of Australia

Before Federation in 1901 five of the six separate colonies maintained their own naval forces for defence. The colonial navies were supported by the ships of the Royal Navy's Australian Station which was established in 1859. The separate colonies maintained control over their respective navies until 1 March 1901, when the Commonwealth Naval Forces was created.

As mounted in bow of Gayundah, 1903 HMCS Gayundah bow view AWM 300016.jpg
As mounted in bow of Gayundah, 1903

Mk VII guns armed the following Australian colonial gun vessels :

HMQS <i>Gayundah</i>

HMQS Gayundah was a flat-iron gunboat operated by the Queensland Maritime Defence Force and later the Royal Australian Navy. She entered service in 1884 and was decommissioned and sold to a civilian company in 1921. She then served as sand and gravel barge in Brisbane until the 1950s, when she was scrapped. In 1958, Gayundah was run aground at Woody Point near Redcliffe, to serve as a breakwater structure.

HMAS <i>Protector</i> (1884)

HMCSProtector was a large flat-iron gunboat commissioned and purchased by the South Australian government in 1884, for the purpose of defending the local coastline against possible attacks in the aftermath of the 'Russian scare', of the 1870s. She arrived in Adelaide in September 1884 and subsequently served in the Boxer Rebellion, World War I and World War II.

HMVS Albert was a gunboat of the Victorian Naval Forces which was requisitioned for service with the Royal Australian Navy during World War I.

Coast defence gun

At Fort Queenscliff, Victoria, Australia BL 8 inch Disappearing Gun Fort Queenscliff VIC.JPG
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.

Disappearing gun

A disappearing gun, a gun mounted on a disappearing carriage, is an obsolete type of artillery which enabled a gun to hide from direct fire and observation. The overwhelming majority of carriage designs enabled the gun to rotate backwards and down behind a parapet, or into a pit protected by a wall after it was fired; a small number were simply barbette mounts on a retractable platform. Either way, retraction lowered the gun from view and direct fire by the enemy while it was being reloaded. It also made reloading easier, since it lowered the breech to a level just above the loading platform, and shells could be rolled right up to the open breech for loading and ramming. Other benefits over non-disappearing types were a higher rate of repetitive fire and less fatigue for the gun crew.

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

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.

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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.
  2. 1 2 3 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
  9. ↑ Northcote's cannons - defending the neighbourhood Darebin Heritage

Bibliography

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