BL 5.5-inch Mk I naval gun

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BL 5.5-inch Mark I
One of HMS Chester's 5.5-inch guns at the Imperial War Museum, London[1]
TypeNaval gun, Coastal defence
Place of originUK
Service history
In service1913–1954
WarsWorld War One
World War Two
Production history
DesignerCoventry Ordnance Works
ManufacturerCoventry Ordnance Works
No. built81
Weight13,955 lbs (6,330 kg)[2]
Length6.985 metres (275.0 in) bore (50 cal)

Shell82 pounds (37.19 kg)
Calibre5.5-inch (140 mm)
BreechWelin breech block with Holmstrom mechanism[3]
Elevation-7 degrees to +30 degrees depending on mount[2]
Rate of fire12 rounds per minute
Muzzle velocity2,790 f/s (850 m/s)[2]
Effective firing range16,250 m at 30-degree elevation

The Breech Loading 5.5-inch Mk I was a naval gun used by the British Royal Navy during both World Wars.

Naval history[edit]

This weapon was developed by Coventry Ordnance Works in 1913 and offered to the Greek Navy as main armament for two new cruisers building at Cammell Laird. On the outbreak Of World War I the two ships were purchased by Britain as HMS Chester and HMS Birkenhead. The RN was happy with the performance of the gun as it was significantly lighter than the standard 6 inch gun and fired an 82 lb shell rather than the 100 lb shell of the 6 inch weapon. It therefore had a higher rate of fire with little loss in hitting power. The British ordered more guns as secondary armament for HMS Furious and HMS Hood. A total of 81 guns were made and were used on the following ships: HMS Chester, HMS Birkenhead, HMS Furious, HMS Hood, and HMS Hermes.

Guns removed from Chester, Birkenhead and Furious were used to arm Armed Merchant cruisers: HMS Laurentic and HMS Montclare.

Coast defence gun[edit]

In 1940, the 5.5 inch guns were removed from HMS Hood in a refit. Two were installed in Hood Battery on Ascension Island and remain there today. A pair were installed in specially built casemates on the roof of Coalhouse Fort in Essex, overlooking the Thames.[4] Guns from the Hood also went to Bognor Regis, Pevensey, North Foreland, Dover and Folkestone.[5]

Notable actions[edit]

The gun Jack Cornwell served in his Victoria Cross action on the forecastle of HMS Chester

Boy Seaman First Class Jack Cornwell was posthumously awarded the Victoria Cross for heroism in serving his gun on HMS Chester during the Battle of Jutland on 31 May 1916.

British 5.5-inch naval gun from World War II at Skansin fortress, Tórshavn, Faroe Islands

Surviving examples[edit]

See also[edit]

Weapons of comparable role, performance and era[edit]


  1. ^ a b Imperial War Museum (2012). "Naval BL 5.5 in Mk I Gun with Mk I pedestal mount". Imperial War Museum Collections Search. Retrieved 6 February 2012.
  2. ^ a b c Campbell, Naval Weapons of WWII, p.40.
  3. ^ Di Giulian
  4. ^ English Heritage (2008). "PastScape: Coalhouse Fort". National Monuments Record: PastScape. English Heritage. Archived from the original on 2 November 2013. Retrieved 10 February 2012.
  5. ^ HMS Hood Association (4 April 2010). "HMS Hood Technical Specifications & Armament Information: Secondary/Dual Purpose Guns". Retrieved 10 February 2012.



  • Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4.

External links[edit]