BL 6-inch Mk VII naval gun

The BL 6 inch Gun Mark VII (and the related Mk VIII) 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The gun superseded the QF 6-inch gun of the 1890s, a period during which the Royal Navy had evaluated QF technology (i.e. loading propellant charges in brass cartridge cases) for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.

Naval gun
The gun was introduced on the s of 1898 (commissioned September 1901) and went on to equip many capital ships, cruisers, monitors, and smaller ships such as the which served throughout World War II.

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 : 
 * s laid down 1898
 * s laid down 1898
 * s laid down 1899
 * s laid down 1899
 * s laid down 1899
 * s laid down in 1901
 * s HMS Commonwealth (1903), HMS Dominion (1903), HMS Hindustan (1903), HMS King Edward VII, HMS New Zealand (1904) laid down 1902
 * cruisers laid down 1902
 * HMS Tiger (1913), battlecruiser laid down 1912
 * s as re-gunned in 1902
 * s laid down 1912
 * s as re-gunned in 1914 with guns from HMS Montagu (1901)
 * HMS M27 of 1915
 * s 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 GERMAN BATTLESHIP Scharnhorst and GERMAN BATTLESHIP Gneisenau in November 1939, and HMS Jervis Bay which similarly sacrificed herself to save her convoy from the 11-inch cruiser GERMAN CRUISER Admiral Scheer in November 1940.

World War I field gun
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.

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.

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".

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
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 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. 

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 SMS Seydlitz and SMS Moltke (11 inch guns) and SMS 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.

Surviving examples

 * 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).
 * 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
 * Mk VII gun dated 1902 at Ile aux Aigrettes, Mauritus
 * 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.