BL 6-inch Mk XIII – XVIII naval gun

Type	Naval gun
Place of origin	United Kingdom
Service history
In service	1914 - 1940s
Wars	World War I World War II
Production history
Designer	Mk XIII, XVII, XVIII : EOC; Mk XIV, XV, XVI : Vickers
Variants	Mk XIII, XIV, XV, XVI, XVII, XVIII
Specifications
Barrel length	300 inches (7.620 m) bore (50 cal)
Shell	100 pounds (45.36 kg)
Calibre	6 inches (152.4 mm)
Muzzle velocity	Mk XIII : 2,770 feet per second (840 m/s); Mk XIV & XV : 2,900 feet per second (880 m/s); Mk XVI : 3,000 feet per second (910 m/s); Mk XVII : 2,905 feet per second (885 m/s); Mk XVIII : 2,874 feet per second (876 m/s)

This article covers a number of fairly similar British-built 6-inch 50-calibre naval guns that found their way into temporary British service in World War I. Their specifications and performance differed from standard Royal Navy 6-inch guns but in British service they fired standard service 100-pound projectiles.

6-inch Mark XIII gun in Royal Navy service

When World War I began, Armstrong-Whitworth were completing the battleship Sultan Osman I for the Ottoman Empire, originally begun as Rio de Janeiro for Brazil. Its secondary armament consisted of 20 of their 6-inch 50 calibre guns, which were similar in design and characteristics to the British naval service Mk XI gun and used the same ammunition. The battleship was completed as HMS Agincourt and served in the Royal Navy in World War I, with its guns designated BL 6 inch Mk XIII.

After the decommissioning of Agincourt in 1921 her 6-inch guns were used for coastal defence, and in 1939 the British gunboats Aphis and Ladybird each had their 2 6-inch Mk VII guns replaced with 2 MK XIII guns, in which capacity they served in World War II.

6-inch Mark XIV and XV guns in Royal Navy service

HMS *Mersey* early in World War I with original twin 6-inch gun turret forward

When World War I began, the Royal Navy had just taken possession of 3 river monitors originally built by Vickers for Brazil but which Brazil could not pay for. These were each equipped with 2 Vickers 6-inch 50-calibre guns in a twin turret, and became the Humber-class monitors. These guns were very similar to the British service Mk XI gun, and in UK service they were designated BL 6 inch Mk XIV (right-hand gun, with breech opening to the right) and BL 6 inch Mk XV (left-hand gun, with breech opening to the left). The guns of HMS Severn and HMS Mersey wore out early in the war from continuous use bombarding the Belgian coast and in East Africa, and were replaced by standard 6-inch Mk VII guns, while HMS Humber continued to use various refurbished Mk XIV and XV guns throughout the war for coastal bombardment.

6-inch Mark XVI gun in Royal Navy service

At the beginning of World War I the British Government forcibly acquired the battleship Reshadieh which Vickers had just completed for the Ottoman Government. The ship entered service with the Royal Navy as HMS Erin together with its armament which while of similar calibre to British service ordnance was of differing specification. Erin had sixteen 6-inch 50 calibre guns made by Vickers, with a muzzle velocity of 3,000 feet per second (910 m/s)^[2] which was considerably greater than existing standard Royal Navy 6-inch guns. These guns were designated 6-inch BL Mark XVI in British service. Some were redeployed in World War II for coast defence.

6-inch Mark XVII gun in Royal Navy service

HMS *Eagle* in 1942 with two starboard forward 6-inch guns visible

When World War I began, Armstrong-Whitworth were building the battleships Almirante Latorre and Almirante Cochrane for Chile. They were acquired by the British government and completed as the battleship HMS Canada and the aircraft carrier HMS Eagle. The secondary armament for each supplied by Armstrongs were 12 6-inch 50-calibre guns, which were designated 6-inch BL Mk XVII in British service. These guns were used from 1915 on HMS Canada until she was sold to Chile in 1920 as originally intended. HMS Eagle was completed after World War I and retained by the Royal Navy, with these guns retained as her primary defensive armament.

6-inch Mark XVIII gun in Royal Navy service

When World War I began, Armstrong-Whitworth were building the coast defence ships Nidaros and Bjørgvin for Norway. They were acquired by the British government and completed as the monitors HMS Gorgon and HMS Glatton respectively. Their secondary armament as designed was 4 15-cm guns designed by Armstrongs. In Royal Navy service these guns were relined to the standard British 6-inch calibre and they were adapted to fire standard 6-inch 100-pound shells.

Notes

^ Mk XIII = Mark 13, Mk XIV = Mark 14, Mk XV = Mark 15, Mk XVI = Mark 16, Mk XVII = Mark 17, Mk XVIII = Mark 18. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence these were the thirteenth through to eighteenth models of BL 6-inch guns in British service.
^ Tony DiGiulian, British 6"/50 (15.2 cm) BL Mark XVI

References

Tony DiGiulian, British 6"/50 (15.2 cm) BL Mark XIII
Tony DiGiulian, Britain 6"/50 (15.2 cm) BL Mark XIV 6"/50 (15.2 cm) BL Mark XV
Tony DiGiulian, British 6"/50 (15.2 cm) BL Mark XVII 6"/50 (15.2 cm) BL Mark XXI
Tony DiGiulian, British 6"/49 (15.2 cm) BL Mark XVIII

External links

[1] Mk XIII = Mark 13, Mk XIV = Mark 14, Mk XV = Mark 15, Mk XVI = Mark 16, Mk XVII = Mark 17, Mk XVIII = Mark 18. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence these were the thirteenth through to eighteenth models of BL 6-inch guns in British service.

[2] Tony DiGiulian, British 6"/50 (15.2 cm) BL Mark XVI

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v t e British Empire naval weapons of the First World War
Monitor guns	BL 9.2-inch Mk VI BL 9.2-inch Mk VIII BL 9.2-inch Mk X BL 9.2-inch Mk XII BL 12-inch Mk VIII BL 14-inch Mk II (US built) BL 15-inch Mk I BL 18-inch Mk I
Capital ship main armament	Vickers 10-inch 45 cal. EOC 10-inch 45 cal. BL 12-inch Mk VIII BL 12-inch Mk IX BL 12-inch Mk X BL 12-inch Mk XI & XII EOC 12-inch 45 cal. Mk XIII BL 13.5-inch Mk I – IV BL 13.5-inch Mk V BL 13.5-inch Mk VI EOC 14-inch 45 cal. Mk I BL 15-inch Mk I
Armoured cruiser main armament	BL 7.5-inch Mk I BL 9.2-inch Mk X BL 9.2-inch Mk XI
Secondary armament and light cruiser main armament	QF 12-pounder 18 cwt QF 14-pounder Maxim-Nordenfelt QF 14-pounder Mk I & II QF 4-inch Mk III BL 4-inch Mk VII QF 4-inch Mk V BL 4-inch Mk IX BL 5.5-inch Mk I QF 6-inch Mk I – III BL 6-inch Mk VII BL 6-inch Mk XI BL 6-inch Mk XII BL 6-inch Mk XIII-XVIII BL 7.5-inch Mk II – Mk V
Destroyer and small cruiser armament	QF 12-pounder 12 cwt Mk II QF 4-inch Mk III BL 4-inch Mk VIII QF 4-inch Mk IV BL 4.7-inch Mk I
Merchant ship armament	QF 4.7-inch Mk I – IV QF 4.7-inch Mk V*
Submarine guns	BL 4-inch Mk XI QF 4-inch Mk XII
Anti-aircraft guns	QF 2-pounder "pom-pom" Mk II QF 3-inch 20 cwt QF 4-inch Mk V
Light weapons	.303 Vickers machine gun QF 3-pounder Hotchkiss QF 3-pounder Vickers QF 6-pounder Hotchkiss
Torpedoes	18-inch Mk V – VIII 21-inch Mk II 21-inch Mk IV
Mines	Spherical Mk I, II and III Vickers Elia mine Type H mine
Anti-submarine weapons	Type A Depth charge Type B Depth charge Type C Depth charge Type D Depth charge Type E Depth charge Type F Depth charge Type G Depth charge Cruiser Mine 7.5-inch howitzer
Landing guns	QF 12-pounder 8 cwt