BL 6-inch Mk VII naval gun

BL 6-inch gun Mk VII
Aboard HMCS Prince David circa 1941
Type	Naval gun Coastal defence gun Heavy field gun
Place of origin
Service history
In service	1901–72 (Fort Scratchley) 1915–18 (field use)
Wars	World War I World War II
Production history
Designer	Vickers
Designed	1899
Number built	898
Variants	Mk VII, Mk VII^v, Mk VIII, Mk XXIV
Specifications
Weight	16,875 lb (7,654 kg) (gun & breech)^[1] 25 tons (gun on field carriage)
Length	279.228 inches
Barrel length	269.5 in (6.85 m) (44.9 cal)
Crew	9

Shell	Lyddite, HE, Shrapnel 100 lb (45 kg)^[2]
Calibre	6 in (152 mm)
Breech	Welin interrupted screw
Recoil	16.5 in (419 mm)
Rate of fire	8 rpm^[3]
Muzzle velocity	2,525 ft/s (770 m/s) (light charge) 2,775 ft/s (846 m/s) (heavy charge)^{[note 1]}
Maximum firing range	Field carriage Mk. II : 13,700 yd (12,500 m)^[4] Naval : 14,600 yd (13,400 m) (light charge); 15,800 yd (14,400 m) (heavy charge)^[5]^{[note 2]}
Filling weight	Lyddite : 13 lb 5 oz (6.0 kg) Amatol : 8 lb 14 oz (4.0 kg) Shrapnel : 874 balls @ 27/lb^[6]

The BL 6 inch Gun Mark VII (and the related Mk VIII)^{[note 3]} was a British naval gun dating from 1899, which was mounted on a heavy traveling carriage in 1915 for British Army service to become one of the main heavy field guns in the First World War, and also served as one of the main coast defence guns throughout the British Empire until the 1950s.

Background

The gun superseded the QF 6-inch gun of the 1890s, a period during which the Royal Navy had evaluated QF technology (i.e. loading propellant charges in brass cartridge cases) for all classes of guns up to 6 inch to increase rates of fire. BL Mk VII returned to loading charges in silk bags after it was determined that with new single-action breech mechanisms a 6-inch BL gun could be loaded, vent tube inserted and fired as quickly as a QF 6 inch gun. Cordite charges in silk bags stored for a BL gun were also considered to represent a considerable saving in weight and magazine space compared to the bulky brass QF cartridge cases.^[7]

Naval gun

Forward starboard casemate guns on HMS Kent showing shell damage sustained in the Battle of the Falkland Islands

Gun drill on troop ship RMS Laconia in March 1942 (World War II)

The gun was introduced on the Formidable-class battleships of 1898 (commissioned September 1901) and went on to equip many capital ships, cruisers, monitors, and smaller ships such as the Insect-class gunboat which served throughout World War II.^[5]

Mk VIII in Naval service was identical to Mk VII, except that the breech opened to the left instead of to the right, for use as the left gun in twin turrets.

Guns were mounted in the following ships :

Formidable-class battleships laid down 1898
Cressy-class cruisers laid down 1898
Duncan-class battleships laid down 1899
Drake-class cruisers laid down 1899
Monmouth-class cruisers laid down 1899
Challenger-class cruisers laid down in 1901
King Edward VII-class battleships HMS Commonwealth, HMS Dominion, HMS Hindustan, HMS King Edward VII, HMS New Zealand laid down 1902
Devonshire-class cruisers laid down 1902
HMS Tiger, battlecruiser laid down 1912
Centurion-class battleships as re-gunned in 1902
Iron Duke-class battleships laid down 1912
Humber-class monitors as re-gunned in 1914 with guns from HMS Montagu
M15-class monitor HMS M27 of 1915
Insect-class gunboats of 1915

In World War II the gun was used to arm British troop ships and Armed Merchant Cruisers, including HMS Rawalpindi, which briefly fought the German 11-inch gun battlecruisers Scharnhorst and Gneisenau in November 1939, and HMS Jervis Bay which similarly sacrificed herself to save her convoy from the 11-inch pocket battleship Admiral Scheer in November 1940 .

World War I field gun

Media related to BL 6 inch Mk VII field gun at Wikimedia Commons

Original Percy Scott field carriage

They were first sent to France in 1915 mounted on improvised rectangular-frame field carriages designed by Admiral Percy Scott, based on the design he had improvised for 4.7-inch guns in the Second Boer War, and were successful.^[8]

However, elevation and hence range was limited with the Scott carriages so a proper carriage, MK II, was introduced early in 1916, allowing elevation to 22°. Carriages Mks III, V and VI also appeared.

Firing near Beaumetz-lès-Loges, cutting wire for the Australian advance Second Battle of Bullecourt 21 April 1917

Night Firing at Vimy Ridge.

It was operated by the Royal Garrison Artillery, as were all the larger guns, in World War I, in batteries of 4 guns.

Following its successful employment in the Battle of the Somme its role was defined as counter-battery fire and also they "were most effective for neutralising defences and for wire cutting with fuze 106 [a new fuze which reliably burst instantly above ground on even slight contact, instead of forming craters]", also for long-range fire against "targets in depth".^[9]

It was superseded by the lighter and longer-range BL 6-inch Gun Mk XIX which was introduced from October 1916 but the Mk VII remained in service to the end of World War I.

Coast defence gun

Media related to BL 6 inch Mk VII coast defence gun at Wikimedia Commons

Bastions C and D of the Keep at the Royal Naval Dockyard on Ireland Island, Bermuda, with two BL 6-inch Mk VII.

Mk VII with a concrete hood at Fort Nepean in 1943.

One two 6-inch Mk VIIs, and two 9.2-inch Mk. Xs, at St. David's Battery, Bermuda, in 2011

Gun on typical coast mounting at Newhaven Fort

The 6-inch Mk VII gun, together with the 9.2-inch Mk X gun, provided the main coast defence throughout the British Empire, from the early 1900s until the abolition of coast artillery in the 1950s. Many guns were specially built for army coast defence use, and following the decommissioning of many obsolete cruisers and battleships after World War I, their 6-inch Mk VII guns were also recycled for coast defence.

103^[10] of these guns were in service in World War I in coastal defences around the UK. Some of these, together with others at ports around the wider British Empire, played an important defence role in World War II and remained in service until the 1950s.

A number of new similar guns with stronger barrels which allowed more powerful cordite charges to be used were manufactured for coast defence during World War II, and were designated 6-inch BL Mark XXIV.^[11]

Notable actions

In the German raid on Scarborough, Hartlepool and Whitby on 16 December 1914, a notable action was fought by Durham Company RGA of the Territorial Force at Heugh (2 guns) and Lighthouse (1 gun) batteries defending Hartlepool. They duelled with the German battlecruisers Seydlitz and Moltke (11 inch guns) and Blücher (8.2 inch), firing 112 rounds and scoring 7 hits. The battlecruisers fired a total of 1,150 rounds at the town and the batteries causing 112 civilians and 7 military killed.^[12]

World War I Ammunition


Mk III 23 lb (10 kg) Cordite MD Cartridge	Mk IV Common lyddite shell	Mk VIIA Common lyddite naval shell	MK XIIA QNT Common lyddite naval shell with night tracer	Mk IX Shrapnel shell	Mk XVI HE shell

Surviving examples

At the Royal Artillery Museum, London

At the Royal Artillery Museum Woolwich, London.
A coast defence gun at Newhaven Fort, Sussex, UK
A gun mounted on the 1904 coast defence emplacement at New Tavern Fort, Gravesend, UK
2 coast defence Mk 7 guns at Fort Dunree, Lough Swilly, in County Donegal, Ireland
St. David's Battery, St. David's Head, St. David's Island, Bermuda. Two Mk VII RBLs, built by Vickers, on Central Pivot Mk II mounts.
Fort St. Catherine's, St. George's Island, Bermuda 6-inch BL Gun Mk VII Gun, built by Vickers, on Central Pivot Mk II mount.
Warwick Camp, Warwick, Bermuda. Two Mk. VII, built by Vickers, on Central Pivot Mk II mounts. (This is an active military base, and the battery is not accessible by the public. The barrels have reportedly been removed, recently, for remounting on the bastions of the Keep, at the Royal Naval Dockyard, on Ireland Island, which houses the Bermuda Maritime Museum.
Royal Naval Dockyard, Ireland Island, Bermuda. Two Mk VII (L/1029 and RGF) on Central Pivot Mk II, at Bastions C and D of the Keep (fortress) which houses the Bermuda Maritime Museum (there is also one BL 6-inch Gun Mk II and one BL 6-inch gun Mk IV, at Bastion E).^[13]^[14]
A gun on field carriage at The Front Museum, Lappohja, Finland
Fort Ogilvie, Point Pleasant Park, Halifax, Nova Scotia
VSM gun No. 1553 dated 1901 at Princess Royal Fortress, Albany, Western Australia. Obtained from Bermuda during restoration of the site in the 1980s.
Barrel 1489 which fired the first Australian shot of WWI, and 1317 which fired the first Australian shot of WWII at Fort Nepean, Victoria

7th Coastal Artillery Battery (Portugal)

Mk VII gun dated 1902 at Ile aux Aigrettes, Mauritius
Momi, Vuda, Batteries, Viti Levu, Fiji Islands. One of the barrels is #1266 from 1900
Fort Mitchell, Spike Island, Ireland, 2 Mk VII Guns in casemates on Central Pivot Mk II mounts in good condition and in the process of being restored to full working condition.
Lonehort Fort, Bere Island, County Cork, Ireland- Two 6 inch BL guns are extant- Breech blocks are missing and the guns themselves somewhat rusty, but otherwise appear to be in good condition. The fort was open to the public on 14/03/14 and 15/03/14 for an underground art experience titled "Nest", which took place in the shell rooms below the guns. The shell rooms and hoists are also in good condition.
Coastal Artillery Battery at Outão, Portugal on the mouth of Sado river, protecting Setubal harbour with 3 guns decommissioned in 1998

Notes

↑ 2,525 ft/s firing a 100 lb (45 kg) projectile using 23 lb (10 kg) Cordite MD size-16 propellant; 2,775 ft/s using 28 pounds 10 ounces (13.0 kg) Cordite MD size 26 was the standard naval loading in WWI. Twin mounts and unstrengthened P IV mounts were restricted to the light charge (Treatise on Ammunition 1915). The original loading was 20 lb (9.1 kg) of the more powerful cordite Mk I size 20, but Mk I caused greater wear
↑ All figures for 100 lb (45 kg) shell, which was standard in WWI.
↑ Mk VII = Mark 7, Mk VIII = Mark 8. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Mark VIII's breech opened to the left and Mark VII's opened to the right, allowing for paired mounts. Guns mounted singly were all the right-opening Mark VII

References

↑ 7 tons, 10 cwt, 2 qtrs. 19 lbs with breech fitting, including shot guide
↑ Shell weights given are filled and fuzed i.e. as fired. 100 lb (45 kg) was standard shell weight in WWI. Some earlier shells had slightly higher weights e.g. Mk IV common lyddite shell weighed 101 lb (45.81 kg)
↑ 8 rounds per minute is the figure given by Vickers. Quoted in Brassey's Naval Annual 1901
↑ Clarke page 23 quotes 13,700 yd (12,500 m) on the Mk II carriage; General Farndale page 130 quotes 12,000 yd (11,000 m) – this is possibly on the Mk I carriage.
1 2 Tony DiGiulian, British 6"/45 (15.2 cm) BL Mark VII
↑ Figures for WWI field gun. Hogg & Thurston 1972, Page 243
↑ Treatise on Ammunition 10th Edition 1915, page 393
↑ Hogg & Thurston 1972, Page 144
↑ Farndale 1986 page 158, quoting War Office Artillery Notes No. 4 – Artillery in Offensive Operations, January 1917.
↑ Farndale 1988, Page 404
↑ DiGiulian
↑ Farndale 1988, Pages 368–369, 401.
↑ The Bermuda Maritime Museum; Guns and Defences
↑ Surviving American Seacoast Artillery Weapons. Compiled: Lists in CDSG News/Journal prepared by C.L. Kimbell (1985), R.D. Zink (1989), and T.C. McGovern (1992 and 1996) (Google document reader)

Bibliography

Handbook for The 6-Inch Breech Loading Mark XII Gun, 1917. G. 21117/17 (PDF). Admiralty, Gunnery Branch, UK. 1917.
Dale Clarke, British Artillery 1914–1919. Heavy Artillery. Osprey Publishing, Oxford UK, 2005 ISBN 978-1-84176-788-8
Tony DiGiulian, British 6"/45 (15.2 cm) BL Mark VII 6"/45 (15.2 cm) BL Mark VIII 6"/45 (15.2 cm) BL Mark XXIV
General Sir Martin Farndale, History of the Royal Regiment of Artillery. Western Front 1914–18. London: Royal Artillery Institution, 1986. ISBN 978-1-870114-00-4
General Sir Martin Farndale, History of the Royal Regiment of Artillery. The Forgotten Fronts and the Home Base, 1914–18. London: Royal Artillery Institution, 1988. ISBN 978-1-870114-05-9
I.V.Hogg & L.F. Thurston, British Artillery Weapons & Ammunition 1914–1918. London: Ian Allan, 1972. ISBN 978-0-7110-0381-1
Admiral Percy Scott, "Fifty Years in the Royal Navy" published 1919

External links

Wikimedia Commons has media related to BL 6 inch Mk VII naval gun.

Terry Gander, Twentieth century British coast defence guns

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 Empire Small Arms & Ordnance of the First World War

No. 1
No. 2 Hales Pattern
Nos. 3, 20, 24, 35 Hales rifle grenades
Nos. 5, 23, 36 Mills
No. 6
Nos. 8, 9 Jam Tin
No. 13 Battye
No. 14 Pitcher
No. 15 Ball
No. 16 Oval
No. 17 Opera hat
No. 18
No. 19
No. 21 "Spherical"
No. 22 Newton-Pippin
No. 25 Sangster
No. 27
No. 28 Chemical
No. 29 Gas
No. 31 Day Signal
No. 32 Night Signal
No. 32 "Spherical E"
No. 34 Egg
No. 37
No. 39 Steuart Pattern

Artillery

Tank guns	QF 6 pounder Hotchkiss QF 6 pounder 6 cwt

Infantry guns	1.59-inch Breech-Loading Vickers Q.F. Gun, Mk II ("Vickers-Crayford rocket gun")

Field Artillery	BL 12 pounder 6 cwt QF 12 pounder 8 cwt QF 12 pounder 18 cwt QF 13 pounder BL 15 pounder BLC 15 pounder QF 15 pounder QF 18 pounder QF 4 inch gun Mk III BL 4 inch gun Mk VII QF 4.5 inch Howitzer

Mountain artillery	RML 2.5 inch Mountain Gun BL 10 pounder Mountain Gun BL 2.75-inch Mountain Gun QF 2.95 inch Mountain Gun QF 3.7-inch mountain howitzer

Howitzers, medium, and heavy artillery	QF 4.7 inch Gun BL 5 inch Howitzer BL 5.4 inch Howitzer BL 60 pounder gun BLC 6 inch siege gun BL 6 inch Gun Mk VII BL 6 inch Gun Mk XIX BL 6-inch 26 cwt howitzer BL 6-inch 30 cwt howitzer BL 8 inch Howitzer Mk I - V BL 8 inch Howitzer Mk VI - VIII

Siege artillery	BL 7.5 inch Mk III naval gun BL 9.2-inch howitzer BL 9.2 inch Mk X naval gun BL 12 inch Howitzer BL 12 inch Mk X naval gun BL 15 inch Howitzer

Coastal artillery	QF 4 inch naval gun Mk I – III BL 6 inch Mk VII naval gun BL 9.2 inch gun Mk IX–X RML 9 inch

Mortars

Grenade launchers

Smoke and chemical weapons

Railway guns

Anti-aircraft guns

Foreign weapon designs
in British Empire Armies use

British Commonwealth artillery of World War II

Tank guns	QF 2 pounder QF 3 pounder QF 6 pounder QF 75 mm QF 3 inch Howitzer QF 17 pounder 77 mm HV QF 95 mm Howitzer

Anti-tank guns	QF 2 pounder QF 6 pounder QF 17 pounder

Field guns and howitzers	75 mm Gun M1917 QF 18 pounder 25 pounder Gun-Howitzer 25 pounder Short QF 4.5-inch howitzer

Medium and Heavy guns and howitzers	BL 4.5-inch Medium Field Gun BL 60-pounder gun BL 5.5-inch Medium Gun BL 6 inch Howitzer BL 6-inch Gun Mk XIX 155 mm Long Tom BL 7.2-inch howitzer BL 8 inch Howitzer BL 9.2-inch howitzer 240 mm howitzer M1

Mountain guns	75mm Pack Howitzer M1 3.7 inch Mountain Howitzer

Mortars	SBML 2inch Mortar ML 3-inch Mortar ML 4.2 inch Mortar

Anti-aircraft weapons	Z Battery 20 mm Oerlikon 20 mm Polsten QF 1½-pounder Mk III QF 2-pounder naval gun Bofors 40 mm QF 3 inch QF 3.7 inch QF 4.5 inch Mk II QF 5.25 inch Mk II

Coast defence	QF 6 pounder 10 cwt QF 12 pounder QF 4.7-inch Mk I–IV BL 6 inch Mk VII & Mk XXIV BL 7.5 inch Mk VI BL 8 inch Mk VIII BL 9.2 inch Mk X BL 14 inch Mk VII BL 15 inch Mk I

Railway artillery	BL 9.2 inch Mk XIII railway gun BL 12 inch Mk V railway howitzer BL 18 inch railway howitzer

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