BL 4.7 inch /45 naval gun

BL 4.7 inch (120 mm) 45 calibre naval gun
"A" gun on destroyer HMAS Stuart, circa. 1930s
Type	Naval gun
Service history
In service	1918–45
Used by	United Kingdom
Wars	World War I World War II
Production history
Designed	1917
Variants	Mk I, Mk II^{[note 1]}
Specifications
Barrel length	5.4 metres (213 in) bore (45 calibres)

Shell	50 pounds (22.68 kg)^[1]
Calibre	120 millimetres (4.724 in)
Muzzle velocity	814 metres per second (2,670 ft/s)^[2]
Maximum firing range	14,450 metres (15,800 yd)^[3]

The BL 4.7 inch 45 calibres 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.

Description and History

Gunners on destroyer HMS Broke, September 1940

Mk I, of built-up wire-wound construction, went into service beginning in 1918 on destroyers of the new Admiralty type destroyer leader (Scott class) and Thornycroft type leader (Shakespeare class). Some saw service in World War I, but most entered service after the war ended.

It was also mounted on :

Faulknor class destroyer leaders as re-gunned in 1918
Thornycroft and Admiralty Modified W Class destroyers completed 1919 – 1920
Prototype destroyers HMS Ambuscade and HMS Amazon commissioned 1926 & 1927

Mk II was a monobloc-barrel (i.e. single-piece, typical of small-medium World War II guns) gun of similar performance introduced in World War II to replace the worn-out Mk I guns on surviving ships.

These were the only BL-type 4.7 inch guns in British service, all others have been of the QF-type. They were superseded on new destroyers from 1930 by the 4.7 inch QF Mark IX.

Ammunition

Mk IIA S.A.P. (semi-armour piercing) shell, 1933

Notes

↑ Mk I = Mark 1, Mk II = Mark 2. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II, and used separate number series for BL and QF guns of the same calibre. Hence these were the first (and only) two models of British BL 4.7-inch guns.

References

↑ DiGiulian
↑ Mk I : 814 m/s : http://navalhistory.flixco.info/H/72400x53535/8330/a0.htm
↑ Mk I : 14450 metres : http://navalhistory.flixco.info/H/72400x53535/8330/a0.htm

Bibliography

Tony DiGiulian, British 4.7"/45 (12 cm) BL Mark I 4.7"/45 (12 cm) BL Mark II

External links

Wikimedia Commons has media related to BL 4.7 inch /45 naval gun.

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 US 14 inch 45 cal 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 V 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 pdr 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 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 pdr 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

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 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 pdr 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 pdr 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)

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