The 50

calibre In guns, particularly firearms, caliber (or calibre; sometimes abbreviated as "cal") is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore match ...

BL 6 inch gun Mark XXIIIMark XXIII = Mark 23. Britain used

Roman numerals Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers are written with combinations of letters from the Latin alphabet, eac ...

to denote Marks (models) of ordnance until after World War II. Mark XXIII indicates this was the twenty-third model of BL 6-inch gun. was the main battery gun used on the

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...

and

British Commonwealth The Commonwealth of Nations, simply referred to as the Commonwealth, is a political association of 56 member states, the vast majority of which are former territories of the British Empire. The chief institutions of the organisation are the Co ...

's conventional (non-anti-aircraft)

light cruiser A light cruiser is a type of small or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck. Prior to thi ...

s built from 1930 through the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, and passed into service with several other navies when ships were disposed of after the end of the War.

Description

The gun replaced the

BL 8 inch Mk VIII naval gun The BL 8 inch gun Mark VIIIMark VIII = Mark 8. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence this was the eighth model of BL 8-inch naval gun. was the main battery gun used on the Royal Navy's ...

used on earlier

Washington Naval Treaty The Washington Naval Treaty, also known as the Five-Power Treaty, was a treaty signed during 1922 among the major Allies of World War I, which agreed to prevent an arms race by limiting naval construction. It was negotiated at the Washington Nav ...

cruisers. These

built-up gun A built-up gun is artillery with a specially reinforced barrel. An inner tube of metal stretches within its elastic limit under the pressure of confined powder gases to transmit stress to outer cylinders that are under tension.Fairfield (1921) p.1 ...

s consisted of a tube and 4.5-metre jacket with a hand-operated

Welin breech block The Welin breech block was a revolutionary stepped, interrupted thread design for locking artillery breeches, invented by Axel Welin in 1889 or 1890. Shortly after, Vickers acquired the British patents. Welin breech blocks provide obturation for ...

. Cloth bags contained 14 kg (30 pound) charges of

cordite Cordite is a family of smokeless propellants developed and produced in the United Kingdom since 1889 to replace black powder as a military propellant. Like modern gunpowder, cordite is classified as a low explosive because of its slow burni ...

or flashless (NQFP) powder for a 51 kg (112-pound) projectile. Useful life of a barrel was 1,100 effective full charges (EFC) with standard cordite and 2,200 EFC with NQFP. The typical maximum rate of fire was eight rounds per gun, per minute. There were three mountings: the two-gun Mk XXI, the three-gun Mk XXII and the three-gun Mk XXIII. Depending on the mount elevation limits differed. The Mk XXI turret elevation limits were +60 degrees to −5 degrees, and the Mk XXII turret elevation limits were +45 degrees to −5 degrees. Loading could be accomplished at any angle up to +12.5 degrees, although the preferred loading angle was between +7 and +5 degrees for all three mounts. The Mk XXI and XXII mounts used a "short trunk" ammunition hoist while the Mk XXIII used a "long trunk" ammunition hoist system, which reduced the crew requirements and increased the speed of the hoists. A RN gunnery officer on HMS ''Bermuda'' gave details of the loading cycle which could be attained in the Mk XXIII turret with a well trained crew: "...a loading cycle of four and a half to 5 seconds was attained at low elevation, another two to three seconds being required with the guns elevated for long range. The time would lengthen as fatigue set in, but was creditable..."Brooke, p.200

Ships mounting BL 6 inch Mk XXIII guns

HMS Orion 6 inch gun crew WWII IWM A 23468

* * * * *

Shell trajectory

Ammunition

HMS Belfast - Gun turret - Shells and tools.jpg,

Surviving examples

* Y turret from , later INS ''Delhi'' (1948), is preserved at the entrance to

Devonport Naval Base Devonport Naval Base is the home of the Royal New Zealand Navy, located at Devonport, New Zealand on Auckland's North Shore. It is currently the only base of the navy that operates ships, and has been in use as a navy base since 1841. The b ...

, Auckland, New Zealand. * A second turret from , is preserved at the

Indian Military Academy The Indian Military Academy (IMA) is one of the oldest military academies in India, and trains officers for the Indian Army. Located in Dehradun, Uttarakhand, it was established in 1932 following a recommendation by a military committee set up ...

Dehradun Dehradun () is the capital and the most populous city of the Indian state of Uttarakhand. It is the administrative headquarters of the eponymous district and is governed by the Dehradun Municipal Corporation, with the Uttarakhand Legislative As ...

. * 12 guns and four turrets are preserved on the museum ship in London, UK * A number of Mark XXIIIs can also be found at English Heritage or other historical sites being used to represent earlier marks which were used as coastal artillery. Tilbury Fort, Essex, has one barrel; Coalhouse Fort, East Tilbury, Essex has two barrels; Gravesend, Kent, has one barrel; the Tynemouth gun emplacement has one barrel. * One is on display at The Historic Dockyard Chatham, Kent, England. It is at the head of No.3 Dry Dock. Royal Navy 6" breech-loading Mk.XXIIIL WWII cruiser gun and the barrel is on 6" P Mk.XI (or P. XII. REGD. No 15) proof mounting as used at Proof and Experimental Establishment (P&EE), Shoeburyness, Essex, 1948-87.

Notes

References

Bibliography

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External links

*Tony DiGiulian
Britain 6"/50 (15.2 cm) BL Mark XXIII
{{DEFAULTSORT:BL 06-inch Mk 23 gun Naval guns of the United Kingdom 152 mm artillery World War II naval weapons of the United Kingdom Military equipment introduced in the 1930s