QF 4.7-inch Mk IX & XII naval gun

The 4.7 inch QF Mark IX and Mark XII[note 1] were 45-calibre, 4.7-inch (120 mm) naval guns which armed the majority of Royal Navy and Commonwealth destroyers in World War II,[1] and were exported to many countries after World War II as the destroyers they were mounted on were sold off.

QF 4.7 inch Mark IX & Mark XII
QF 4.7 inch Mk XII guns HMS Javelin 1940 IWM A 291
A twin Mk.XII mounting on HMS Javelin. The cylindrical Fuse Setting Pedestal is clearly visible on the right, at waist height.
TypeNaval gun
Place of originUnited Kingdom
Service history
In service1928–1970?
Used byRoyal Navy
Royal Canadian Navy
Royal Australian Navy
Royal Hellenic Navy
Royal Netherlands Navy
Polish Navy
Royal Norwegian Navy
Turkish Navy
Dominican Navy
Argentine Navy
Brazilian Navy
WarsWorld War II
Korean War
Production history
No. built742 (Mk IX); 372 (Mk XII)
Mass2.963–2.984 long tons (3,011–3,032 kg) (Mk IX)
3.238–3.245 long tons (3,290–3,297 kg) (Mk XII)
Length220.62 in (5.60 m) (Mk IX)
224.08 in (5.69 m) (Mk XII)
Barrel lengthBore: 212.58 in (5.40 m) L/45 (cal)

ShellSeparate loading cased charge
Shell weight50 pounds (22.7 kg) SAP or HE
Calibre4.724 inches (120 mm)
BreechSemi-automatic horizontal sliding-block
ElevationVaried by mounting
Rate of fireabout 12 rounds per minute
Muzzle velocity2,650 ft/s (810 m/s)
Maximum firing range16,970 yards (15,520 m) at 40°
HMCS Assiniboine bows NF-402
Single Mk IX gun on HMCS Assiniboine with gunners sheltering behind the shield

Description and history

These guns succeeded the similar World War I-era BL 4.7 inch gun, changing the cartridges from BL silk bags to separate QF in brass cases and a new horizontal sliding-block breech mechanism.

Mark IX was deployed in single mountings CP Mk XIV on the A-class destroyers of 1930 and on most subsequent destroyer classes up to and including the R class of 1942.

HMAS Nizam AWM-009410
Twin Mk XII guns on HMAS Nizam

The almost-identical Mk XII gun was deployed in twin mountings CP Mk XIX on the Tribal-class destroyers of 1936 and J, K and N classes of 1938. This mounting limited the maximum elevation to 40 degrees, but all twin CP Mk XIX were dual-purpose mountings and were equipped with Fuze Setting Pedestals or Mk V Fuze Setting Trays,[2] to allow the mountings to be fired against aircraft while being controlled by the Fuze Keeping Clock (FKC) fire control computer. Typical maximum rate of fire was twelve rounds per gun, per minute.[3][4] During gunnery trials in 1930, HMS Basilisk' was able to fire "...five rounds in 17 seconds."[5] The Mk XII gun fired a 50 lb (23 kg) shell and used a separate cartridge, with both shell and cartridge being loaded via a loading tray, with power ramming, elevation, and traverse. The maximum range at 40 degrees elevation was 16,970 yards (15,520 m) fired at the new gun muzzle velocity of 2,650 fps (808 m/s).[1] The 40-degree elevation was justified on the grounds that destroyers would be screening the battle-fleet during aerial attack, and 40 degrees elevation was adequate to engage aircraft that were concentrating their attack on other ships.[6]

Admiral Sir Philip Vian describes the use of Tribal-class destroyer mounted Mk XII guns against aircraft during the campaign in Norwegian waters, from April to June 1940:

"It became clear at once that in an attack from the air in narrow waters flanked by mountains, the cards were held by the aircraft. There was too little sea-room for full freedom of manoeuvre, and the aircraft's approach was screened by the rock walls. As often as not, when they did come into view it was at such an angle that our 4.7-inch guns, whose maximum elevation was only forty degrees, could not reach them... Aandalsnes is approached through the Romsdal Fiord, and lies forty miles from the entrance, off which we arrived on the 24th April. The daylight passage of the convoy and escort through this waterway, speed five knots, on a steady course and with mountains rising steeply either side, presented an alluring invitation to enemy aircraft. Junkers attacks persisted to the end, but the fire of the destroyers, although limited to an elevation of forty degrees, was enough to keep the enemy just too high for their standard of marksmanship. Not a ship received a direct hit, though some were damaged by the splinters from near misses."[7]

The S class, introduced the CP (central pivot) single Mark XXII mounting for the QF Mark XII 4.7 in gun. This new mounting had a shield with a sharply raked front, to allow increased elevation (to 55 degrees),[8][9] contrasting noticeably with the vertical front of the previous CP Mark XVIII, and easily differentiated the S class onwards from their immediate predecessors. Savage was the exception in this respect, being fitted with 4.5 inch calibre; a twin mounting forward and two singles aft.

The 4.7 inch calibre was finally superseded by the 4.5 inch calibre on the Z-class destroyers in 1943. The new 4.5 inch guns all had 55-degree elevation mounts and actually fired a shell slightly heavier than that of 4.7-inch Mk IX and XII guns, although slightly lighter than that fired by the 4.7 inch Mk XI gun.


4.7 inch SAP Mk II A shell diagrams 1933
Mk IIA S.A.P. (semi armour-piercing) shell
Australian naval gunners with 4.7 inch ammunition 1944 AWM 016472.jpeg
Australian gunners with cartridge cases and shell, January 1944

Gun Mounting Data

Mounting[1] Elevation Weight w/o shield Shield Thickness Shield Weight Number of guns
CPXIV -10° to +30°  8.64 tons / 8,781 kg 0.144 in / 3.7 mm 0.85 tons / 864 kg 1
CPXVII -10° to +40°  8.829 tons / 8,971 kg 0.125 in / 3.2 mm 0.85 tons / 864 kg 1
CPXVIII -10° to +40°  9.544 tons / 9,697 kg 0.125 in / 3.2 mm 1.163 tons / 1,182 kg 1
CPXIX -10° to +40°  22.93 tons / 23,298 kg unknown 2.55 tons / 2,591 kg 2
CPXXII -10° to +55°  11.58 tons / 11,766 kg 0.375 in / 9.5 mm 1.813 tons / 1,842 kg 1

Weapons of comparable role, performance and era


  1. ^ Mark IX = Mark 9, Mark XII = Mark 12. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. This article covers the ninth and twelfth models of British QF 4.7 inch gun.


  1. ^ a b c Campbell, Naval Weapons of World War Two, p48.
  2. ^ Hodges and Friedman, Destroyer weapons of WW2, P95-96.
  3. ^ Hodges and Friedman, Destroyer weapons of WW2, p21.
  4. ^ March, British Destroyers, P358, Kimberley at Narvik: "Salvos fired about 180 in all...drill to guns very good, great part of the action a loading interval of about 5 seconds was achieved..."
  5. ^ March, British Destroyers, P264
  6. ^ Harding, editor, The Royal Navy, 1930-2000: innovation and defence, p19-41:, Pugh, Managing the aerial threat.
  7. ^ Vian, Philip, Action This Day, London, 1960, p.40 and 44.
  8. ^ March, British Destroyers, p.401.
  9. ^ Hodges, Tribal Class Destroyers, p32: Diagram of High Level Bomber Attack: A 240 mph target, at 12 thousand feet altitude could expect to be under fire for about 58 seconds, from the time it enters the effective range of the FKC until it flies to within the minimum range of a 4.7-inch gun elevated to 55 degrees. A Tribal class destroyer would be able to engage the same target for about 37 seconds with a 4.7-inch Mk XII gun elevated to 40 degrees.


  • Campbell, John (1985). Naval Weapons of World War II. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-459-4.
  • Hodges, Peter; Friedman, Norman (1979). Destroyer Weapons of World War 2. London: Conway Maritime Press. ISBN 0-87021-929-4.
  • March, Edgar J. (1966). British Destroyers: A History of Development, 1892-1953; Drawn by Admiralty Permission From Official Records & Returns, Ships' Covers & Building Plans. London: Seeley Service. OCLC 164893555.

External links

BL 16-inch Mk I naval gun

The BL 16-inch Mark I was a British naval gun introduced in the 1920s and used on the two Nelson-class battleships. A breech-loading gun, the barrel was 45 calibres long ("/45" in shorthand) meaning 45 times the bore (16 in) – 60 ft (18 m) long.

BL 4-inch Mk IX naval gun

The BL 4-inch Mk IX naval gun was a British medium-velocity naval gun introduced in 1916 as secondary armament on the Renown-class battlecruisers and Glorious-class "large light cruisers", but which served most notably as the main armament on Flower-class corvettes throughout World War II.

BL 4.7-inch 45-calibre naval gun

The BL 4.7-inch, 45-calibre gun (actually a metric 120 mm gun) was a British medium-velocity naval gun introduced in 1918 for destroyers, intended to counter a new generation of heavily armed destroyers that Germany was believed to be developing.

BL 6-inch Mk XII naval gun

The BL 6-inch Mark XII naval gun was a British 45 calibre naval gun which was mounted as primary armament on light cruisers and secondary armament on dreadnought battleships commissioned in the period 1914–1926, and remained in service on many warships until the end of World War II.

BL 6-inch Mk XXII naval gun

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BL 7.5-inch Mk VI naval gun

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Dual-purpose gun

A dual-purpose gun is a naval artillery mounting designed to engage both surface and air targets.

HMAS Quickmatch (G92)

HMAS Quickmatch (G92/D21/D292/F04) was a Q-class destroyer operated by the Royal Australian Navy (RAN). Although commissioned into the RAN in 1942, the ship was initially the property of the Royal Navy. Quickmatch served with both the British Eastern Fleet and British Pacific Fleet during World War II. In the 1950s, the destroyer was converted into an anti-submarine frigate. In 1957, Quickmatch operated in support of Malaya during the Malayan Emergency. The ship remained in service until 1963, and after use as an accommodation ship, was sold for scrap in 1972.

HMS Brazen (H80)

HMS Brazen was a B-class destroyer built for the Royal Navy around 1930. Initially assigned to the Mediterranean Fleet, she was transferred to Home Fleet in 1936. The ship escorted convoys and conducted anti-submarine patrols early in World War II before participating in the Norwegian Campaign in April–May 1940. Brazen later began escorting coastal convoys in the English Channel and was sunk in late July 1940 by German aircraft whilst doing so.

HMS Duchess (H64)

HMS Duchess was a D-class destroyer built for the Royal Navy in the early 1930s. The ship was initially assigned to the Mediterranean Fleet before she was transferred to the China Station in early 1935. She was temporarily deployed in the Red Sea during late 1935 during the Abyssinia Crisis, before returning to her duty station where she remained until mid-1939. Duchess was transferred back to the Mediterranean Fleet just before the Second World War began in September 1939. Whilst escorting the battleship HMS Barham back to the British Isles, she was accidentally rammed by the battleship in thick fog and sank with heavy loss of life on 12 December 1939.

HMS Quality (G62)

HMS Quality (G62/D18) was a Q-class destroyer built for the Royal Navy. Entering service in 1942, the destroyer served in several theatres of World War II. Following the war's conclusion, the ship was transferred to the Royal Australian Navy (RAN), commissioning as HMAS Quality (G62/D262) in late 1945. Unlike her sister ships, which were refitted as anti-submarine frigates, Quality was not modified, decommissioned after only 59 days of service, and was sold for scrap in 1958.

QF 3-pounder Vickers

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QF 4-inch naval gun Mk IV, XII, XXII

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QF 4-inch naval gun Mk XIX

The QF 4-inch Mk XIX gun was a British low-velocity 4-inch 40-calibre naval gun used to arm small warships such as Bathurst and Castle-class corvette and some River-class frigate in World War II, mainly against submarines.

QF 4-inch naval gun Mk XVI

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QF 4.7-inch Mk VIII naval gun

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QF 6-pounder 10 cwt gun

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Unrotated projectile

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Vickers .50 machine gun

The Vickers .50 machine gun, also known as the 'Vickers .50' was similar to the .303 inches (7.70 mm) Vickers machine gun but enlarged to use a larger-calibre 0.5-inch (12.7 mm) round. It saw some use in tanks and other fighting vehicles but was more commonly used as a close-in anti-aircraft weapon on Royal Navy and Allied ships, typically in a four-gun mounting. The Vickers fired British .50 Vickers (12.7×81mm) ammunition, not the better known American .50 BMG (12.7×99mm).

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