Ordnance QF 4 inch gun Mk IV, XII, XXII
Mk IV gun from HMS Lance at Imperial War Museum Naval Gallery in South Kensington, London 1926
Type	Light Naval gun Submarine gun
Place of origin	United Kingdom
Service history
In service	1911-1940s
Used by	United Kingdom
Wars	World War I World War II
Production history
No. built	1,141^[1]
Specifications
Mass	2,750 pounds (1,250 kg) barrel & breech
Barrel length	160 inches (4.064 m) bore (40 calibres)

Shell	Mk IV : Separate QF 31 pounds (14.06 kg); Mk XII & XXII : Fixed QF 31 pounds (14.06 kg), 35 pounds (15.88 kg) from 1944^[2]
Calibre	4-inch (101.6 mm)
Breech	horizontal sliding-block
Elevation	PIX Mount -10° to +20° CPIII Mount -10° to +30°^[1]
Muzzle velocity	Mk IV : 2,370 feet per second (720 m/s)^[3] Mk XII & XXII : 1,873 feet per second (571 m/s)
Maximum firing range	11,580 yards (10,590 m) at +30°^[1]

The QF 4-inch gun Mk IV^{[note 1]} was the main gun on most Royal Navy and British Empire destroyers in World War I. It was introduced in 1911 as a faster-loading light gun successor to the BL 4 inch Mk VIII gun. Of the 1,141 produced, 939 were still available in 1939.^[1] Mk XII and Mk XXII variants armed many British interwar and World War II submarines.

Mk IV gun

Mk IV armed many British destroyers and some cruisers in World War I. It was used to arm merchant ships in World War II.

The guns armed the following warships :

Forward-class scout cruisers as re-gunned in 1911
Sentinel-class scout cruisers as re-gunned 1911-1912
Pathfinder-class scout cruisers as re-gunned 1911-1912
Adventure-class scout cruisers as re-gunned 1911-1912
Acasta (K)-class destroyers of 1911
Laforey (L)-class destroyers of 1913
Yarrow M-class destroyers laid down 1912 - 1915
Admiralty M-class destroyer of 1913
Thornycroft M-class destroyers laid down 1913 - 1915
Hawthorn M-class destroyer of 1914
Talisman-class destroyers of 1914
Medea-class destroyers of 1914
Faulknor-class leaders of 1914
Marksman-class destroyers of 1914
Parker class leaders of 1915
Yarrow Later M-class destroyers of 1915
R-class destroyers of 1916
S-class destroyers of 1917
Fundy-class minesweepers of 1938 (guns from decommissioned Canadian S-class destroyers)

Rusted QF 4 inch mk IV gun without a gun shield on East Falkland
Back of rusted QF 4 inch mk IV gun without a gun shield
Front of QF 4 inch mk IV gun in Imperial War Museum
Back of QF 4 inch Mk IV gun at Imperial War Museum
British sailors loading a QF 4 inch Mk IV gun in 1942
Diagram of a QF 4 inch Mk IV gun cartridge.

Mk XII and XXII submarine gun

The Mk XII variant was developed for arming submarines from 1918, Mk XXII was developed to arm submarines during World War II. These submarine guns fired a heavier 35 pounds (16 kg) projectile from late 1944.^[2] Shortly after the end of hostilities, the Mk XXII was superseded in new British submarines by the lighter QF 4 inch Mk XXIII.^[4]

Mk XII and XXII equipped submarines

Surviving guns

The Mk IV gun from HMS Lance which fired the first British shot of World War I on 5 August 1914 is on display at the National Museum of the Royal Navy, Portsmouth (on loan from the Imperial War Museum).^[5]
A Mk IV gun on a 1945 Mk XVI mounting is on display at the Heugh Gun Battery Museum in Hartlepool, County Durham.^[6]
A Mk IV gun on a pedestal mounting is still in situ at Ordnance Point in the Falkland Islands, where it is believed to have been installed in 1943.^[7]
A First World War 4-inch naval gun, tentatively identified as a Mk IV, stands outside the Army, Navy and Air Force Veterans Hall in 4th Street, Sidney, British Columbia.^[8]

Notes

References

Sources

Tony DiGiulian, British 4"/40 (10.2 cm) QF Marks IV, XII and XXII
Campbell, John (1985). Naval Weapons of World War Two. Annapolis, MD: Naval Institute Press. ISBN 0-87021-459-4.

Wikimedia Commons has media related to QF 4 inch Mk IV naval gun.

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

v t e British Commonwealth naval weapons of the Second World War
Monitor guns	BL 15-inch
Capital ship main armament	BL 14-inch BL 15-inch BL 16-inch
Heavy cruiser main armament	BL 7.5-inch Mk VI BL 8-inch Mk VIII
Secondary armament and light cruiser main armament	QF 4-inch Mk V QF 4.5-inch QF 5.25-inch BL 5.5-inch BL 6-inch Mk XII BL 6-inch Mk XXII BL 6-inch Mk XXIII
Minesweeper, Sloop, Corvette, Frigate and Destroyer armament	QF 6-pounder 10 cwt QF 12-pounder 12 cwt Mk V QF 4-inch Mk IV BL 4-inch Mk IX QF 4-inch Mk XVI QF 4-inch Mk XIX QF 4.5-inch BL 4.7-inch Mk II QF 4.7-inch Mk IX & XII QF 4.7-inch Mk XI
Submarine guns	QF 12-pounder 12 cwt Mk V QF 3-inch 20 cwt QF 4-inch Mk XII & XXII
Anti-aircraft weapons	Unrotated projectile Holman Projector 20 mm Oerlikon QF 2-pounder "pom-pom" Mk VIII 40 mm Bofors QF 3-inch 20 cwt QF 4-inch Mk V QF 4-inch Mk XVI QF 4.5-inch QF 4.7-inch Mk VIII
Light weapons	.303 Lewis machine gun .50 Vickers Mk III machine gun QF 3-pounder Vickers
Torpedoes	21-inch Mk VII 21-inch Mk VIII 21-inch Mk X 21-inch Mk XI 24.5-inch Mk I
Anti-submarine weapons	Thornycroft depth charge thrower Hedgehog Squid
Small craft armament	Molins 6-pounder Vickers K machine gun 18-inch torpedo
Foreign-sourced weapons	20 mm Oerlikon 40 mm Bofors 3-inch 23 caliber gun (US) 3-inch 50 caliber gun (US) 4-inch 50 caliber Mark 9 gun (US) 5-inch 51 caliber Mark 8 gun (US) Y-gun depth charge projector (US) Mark 8 torpedo (US)