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Armstrong BL 6-inch 30 calibre gun
Armstrong cannon, Chulachomklao fort.jpg
Disappearing gun at Fort Chulachomklao, Thailand
Type Coast defence gun
Place of origin United Kingdom
Service history
In service 1884 - 1945[1]
Used by United Kingdom
Australian Colonies
New Zealand
Production history
Designer Elswick Ordnance Company (EOC)
Manufacturer EOC
Unit cost £3,400[2]
Weight 5 tons barrel & breech[3]
Barrel length 183.5 inches (4,661 mm) bore (30.58 calibres);[4]
192 inches (4,877 mm) bore and chamber (32 calibres)[5]

Shell 100 pounds (45.36 kg)[4]
Calibre 6-inch (152.4 mm)
Breech 3 motion interrupted screw. Elswick cup obturation
Muzzle velocity 1,890 feet per second (576 m/s)[6]
Maximum range 8,000 yards (7,300 m)[7]
8,530 yards (7,800 m) (Romanian service)[8]

The BL 6 inch gun Mk V [note 1] was an early Elswick Ordnance Company breech-loading naval gun originally designed to use the old gunpowder propellants. They were used for coast defence around the British Empire.

Description and service

Gun construction and rifling diagram

This was an Elswick Ordnance export design, completely different from and longer (30-calibres, 183.5 inch bore) than the contemporary 26-calibres British naval service 6-inch Mk III, IV and VI guns designed by the Royal Gun Factory, although it fired the same 100-pound projectiles. The gun was of a complex all-steel built-up construction, of a steel A-tube surrounded by multiple steel hoops, breech-piece and jacket.

Several were acquired by the British government for coast defence in the UK and were given the designation 6-inch gun Mark V. The breech fittings and firing mechanism were modified in British service to standardize them with the British service guns, Mark IV and VI. The breech-screw was locked by turning to the left, unlike standard service guns made by the Royal Gun Factory, which all locked to the right. Rifling consisted of 28 grooves of the polygroove "Elswick section" type, increasing from 0 to 1 turn in 30 calibres (i.e. 1 turn in 180 inches) at the muzzle.[9]

Mk V in the upper casemate battery at Georges Head, Sydney, 1892

They were also exported for use as coast-defence guns in Hong Kong, New Zealand, Australian colonies and Siam (Thailand), typically as disappearing guns.

Romania purchased 10 L/32 guns and used them during the First World War. The Romanian guns had a greater range (7,800 meters).[8]

QFC conversion

QFC gun, Albany defences, March 1943

During the 1890s, when the new "QF" technology of loading propellant charges in brass cases to increase the rate of fire was in favour, 4 guns were returned from New South Wales, Australia to the UK to be converted to QF.

2 of the resulting QFC guns are known to have been still in commission until 1945, in the Princess Royal Fortress defending the port of Albany, Western Australia.[10]

Image gallery

See also

Surviving examples


  1. Mk V = Mark 5. Britain used Roman numerals to designate Marks (models) of ordnance until after World War II. Hence this was the fifth model of BL 6-inch gun in British service.


  1. 2 QFC guns were in service until 1945 at Albany, Western Australia
  2. Unit price for 13 Mk V guns 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.
  3. Text Book of Gunnery 1902
  4. 4.0 4.1 Text Book of Gunnery 1902, Table XII
  5. Text Book of Gunnery 1887, Table XVI
  6. Mk V gun is quoted with mv of 1920 feet/second in Text Book of Gunnery 1887, and 1890 ft/sec in the 1902 edition.
  7. Text Book of Gunnery 1902 quotes 10,000 yards for Mks III, IV, VI and 8,000 yards for Mk V.
  8. 8.0 8.1 Sanders Marble, BRILL, 2016, King of Battle: Artillery in World War I, p. 358
  9. "Treatise on Construction of Service Ordnance, 1893", pages 263-264
  10. Peter Dunn, "two emplaced at the fortress from 1938 to 1945. It was originally from South Head - Sydney and was one of the four BL guns from the Colony of NSW which was sent to England in the late part of the 19th Century to be converted to QF"


External links

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