QF 4-inch naval gun Mk VI, X

Ordnance QF 4 inch gun Mk VI, X
Ordnance QF 4 inch gun Mk VI, X
Type	Light naval gun
Place of origin	United Kingdom
Service history
In service	1913–1945
Used by	United Kingdom, Chile
Wars	World War I
Production history
Manufacturer	Elswick Ordnance Company
No. built	29
Specifications
Mass	3,136 lb (1,422 kg)
Length	165.1 in (4,190 mm)
Barrel length	160.1 in (4,070 mm) bore (40 calibres)
Shell	Separate QF
Shell weight	31 pounds (14.1 kg)
Calibre	4-inch (102 mm)
Elevation	PXI Mount +25°
Muzzle velocity	2,300 ft/s (700 m/s)
Maximum firing range	11,630 yards (10,630 m) at +25°

The QF 4-inch gun Mk VI^{[note 1]} was an Elswick Ordnance Company (EOC) design that was used aboard a few British flotilla leaders and smaller warships during the First World War. A similar EOC gun was designated as the QF Mk X.

Mk VI gun

The Mk VI was an EOC "Pattern S" gun that that served as the primary armament of the Chilean Almirante Lynch-class destroyers built during the early 1910s. Four of these ships were still under construction when the war began in August 1914 and were purchased by the Royal Navy where they were known as the Faulknor class. Only 29 guns were built; it's ammunition was incompatible with other British guns. The submarine Swordfish was equipped with the gun after she was converted into a patrol boat in 1918. The Acacia-class sloop Mimosa was also equipped with the weapon.^[1]^[2]

Mk X gun

A single EOC "Pattern Q" gun of similar design was purchased and designated as the Mk X. It is doubtful that it was mounted on a ship.^[3]

Notes

^ Mk VI = Mark 6. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. This was the sixth model of 4-inch QF naval gun.

References

^ Friedman, p. 104
^ Campbell, pp. 118–119
^ Campbell, p. 118

Sources

Campbell, N. J. M. (1986). "British Naval Guns 1880–1945, No 18". In Lambert, Andrew (ed.). Warship X. Conway Maritime Press. pp. 117–120. ISBN 0-85177-449-0.
DiGuilian, Tony. "United Kingdom / Britain 4"/40 (10.2 cm) QF Mark VI and Mark X". Navweaps.com. Retrieved 4 January 2026.
Friedman, Norman (2011). Naval Weapons of World War One: Guns, Torpedoes, Mines and ASW Weapons of All Nations; An Illustrated Directory. Seaforth Publishing. ISBN 978-1-84832-100-7.

[1] Mk VI = Mark 6. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. This was the sixth model of 4-inch QF naval gun.

[2] Friedman, p. 104

[3] Campbell, pp. 118–119

[4] Campbell, p. 118

[note 1]

[1]

[2]

[3]

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 QF 4-inch Mk VI
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