BL 6-inch Mk VII naval gun

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BL 6-inch gun Mk VII
6inchMkVIIGunColouredPostcardWWI.jpg
Field gun at full recoil after firing, Reningelst, Flanders, 15 June 1916. Colourised photograph on propaganda postcard
Type Naval gun
Coastal defence gun
Heavy field gun
Place of origin United Kingdom
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 VIIv, 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)[4]
Maximum firing range Field carriage Mk. II : 13,700 yd (12,500 m)[5] Naval : 14,600 yd (13,400 m) (light charge); 15,800 yd (14,400 m) (heavy charge)[6][7]
Filling weight Lyddite : 13 lb 5 oz (6.0 kg)
Amatol : 8 lb 14 oz (4.0 kg)
Shrapnel : 874 balls @ 27/lb[8]

The BL 6 inch Gun Mark VII (and the related Mk VIII)[9] 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[edit]

The gun superseded the QF 6-inch gun of the 1890s, a period during which the Royal Navy had evaluated QF technology (i.e. loading propellant charges in brass cartridge cases) for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.[10]

Naval gun[edit]

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.[6]

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 :


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 cruiser Admiral Scheer in November 1940 .

World War I field gun[edit]

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.[11]

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".[12]

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[edit]

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[13] 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.[14]

Notable actions[edit]

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.[15]

World War I Ammunition[edit]

BL6inchGunCartridgeMkIII23lb.jpg
6inchMkIVLydditeShell.jpg
BL6inchMkVIILydditeShell.jpg
6inchLydditeMkXIIAQNTShellDiagram.jpg
BL6inchShrapnelShellMkIXDiagram.jpg
BL 6 inch HE Gun Shell Mk XVI Diagram.jpg
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

See also[edit]

Surviving examples[edit]

At the Royal Artillery Museum, London

Notes and references[edit]

  1. ^ 7 tons, 10 cwt, 2 qtrs. 19 lbs with breech fitting, including shot guide
  2. ^ 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)
  3. ^ 8 rounds per minute is the figure given by Vickers. Quoted in Brassey's Naval Annual 1901
  4. ^ 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
  5. ^ 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.
  6. ^ a b Tony DiGiulian, British 6"/45 (15.2 cm) BL Mark VII
  7. ^ All figures for 100 lb (45 kg) shell, which was standard in WWI.
  8. ^ Figures for WWI field gun. Hogg & Thurston 1972, Page 243
  9. ^ 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
  10. ^ Treatise on Ammunition 10th Edition 1915, page 393
  11. ^ Hogg & Thurston 1972, Page 144
  12. ^ Farndale 1986 page 158, quoting War Office Artillery Notes No. 4 – Artillery in Offensive Operations, January 1917.
  13. ^ Farndale 1988, Page 404
  14. ^ DiGiulian
  15. ^ Farndale 1988, Pages 368–369, 401.
  16. ^ The Bermuda Maritime Museum; Guns and Defences
  17. ^ 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[edit]

External links[edit]