Britain 6"/45 (15.2 cm) BL Mark VII and Mark VIII

Britain
6"/45 (15.2 cm) BL Mark VII
6"/45 (15.2 cm) BL Mark VIII
6"/45 (15.2 cm) BL Mark XXIV
Updated 30 January 2009

A Vickers design that was widely used on pre-World War I ships as well as being one of the Army's best artillery weapons once some early teething problems were worked out.

During World War I, these guns were used to arm a variety of Monitors. Used in small gunboats and AMCs during World War II. The Army used them mainly for coastal defense batteries for both wars. Some were used as heavy field artillery during World War I and a few were used as railway guns during World War II.

The only difference between the Mark VII and Mark VIII was that the breech on the Mark VII opened to the right while breech on the Mark VIII opened to the left in order to suit the left hand gun mounting in the twin mounts used on the Monmouth class cruisers.

The Mark VII and VIII were constructed of inner A tube, A tube, partially wire wound, B tube and overlapping jacket. Older guns used a four-motion long-screw breech while later ones used a Welin breech block and hand-worked skew gear mechanism. A total of 898 (one source says 901 guns) Mark VII and 27 Mark VIII guns were built and three Mark VIII guns were converted to the Mark VII style after the Monmouth class cruisers were scrapped. 629 of these guns remained in Navy service as of 1939. Twelve Army guns lacking a B tube were designated as Mark VIIv, while the Mark VII* and VIIv* were guns relined with a high strength alloy steel A tube which allowed heavier charges in the later 45 degree coastal mountings. The total number of guns issued to the Army was about 350 and many more were transferred from the Navy.

The Mark VII remained in service until the abolition of coast artillery in 1956 (Britain) and 1959 (NZ).

The Mark XXIV was an Army coastal defense gun with the same performance as the Mark VII* but with a loose barrel construction. About 140 of these guns were manufactured during World War II.

I believed this to be a 6"/45 (15.2 cm) Mark VII
Note the projectiles on the left, the powder bags on the right and the lack of shoes
Photograph courtesy of Brian Cave and Paul Benyon

Armored Cruiser HMS Good Hope in 1907
The 6" (15.2 cm) guns are in the hull casemates. Note how easily these would become useless in any kind of seaway.
IWM Photograph

Berwick in 1905
Good picture showing the twin turret with both Mark VII and Mark VIII guns and Mark VII guns in hull casemates
IWM Photograph

6"/45 (15.2 cm) Mark VII
This gun was built in 1900 and is now at the Rotunda Artillery Museum, Woolwich
Picture copyrighted by Bob Cordery of Colonial Wargamming

. Images at The Vickers Photographic Archive

See photograph 4902

Gun Characteristics .

Designation	6"/45 (15.2 cm) BL Mark VII 6"/45 (15.2 cm) BL Mark VIII
Ship Class Used On	Mark VII Capital Ships: Formidable, London, Duncan, first five King Edward's, Tiger, Barfleur and Iron Duke classes Cruisers: Cressy, Drake, Monmouth, Hampshire and Challenger classes Monitors: Severn, Humber, Mersey, M.27, Clive, Craufurd, Eugene, Moore, Rupert and Wolfe Gunboats: Aphis class Other: AMCs, some DAMS and auxiliary warships Rearmed: Narcissus, Immortalité, Undaunted, Endymion, Theseus, Edgar, Grafton, Highflyer, Hyacinth, Vindictive, Astraea, Fox, Amethyst, Adventure, Attentive and all Dido class except Eclipse The large destroyer Swift replaced her two bow 4"/40 (10.2 cm) Mark VIII guns with one of these guns Briefly used on the destroyer Viking Schoolboats: Bustard, Cuckoo and Drudge 1919 Caspian Force and Siberia River Flotilla World War II: Iron Duke, Insect class gunboats, AMCs, armed liners and DEMS Mark VIII Monmouth class, schoolboat Drudge and escort ship Discoverer
Date Of Design	1899
Date In Service	1901
Gun Weight	16,572 lbs. (7,517 kg) with breech
Gun Length oa	279.2 in (7.092 m)
Bore Length	269.5 in (6.845 m)
Rifling Length	233.6 in (5.933 m)
Grooves (see Note 1)	24
Lands	N/A
Twist	N/A
Chamber Volume (see Note 2)	1,715 in³ (28.10 dm³)
Rate Of Fire (see Notes 3 and 4)	5 - 7 rounds per minute
Notes: 1) There were two different kinds of rifling in general use, designated as Mark I and Mark III. I have been unable to determine the differences between these two Marks or what was Mark II rifling. 2) The chamber volume for a few guns was altered to allow a larger charge - see notes in the "Ammunition" section below. 3) The Rate of Fire figure given above is found in references for British guns of this caliber, but "Warrior to Dreadnought: Warship Development 1860-1905" quotes Jellicoe's 1906 figures for rates of fire for these guns in gunlayers' tests and in battle practice and notes that the latter figures corresponded well to those actually attained by the Japanese at Tsushima: Gunlayers Test: 12 rounds per minute Battle Practice: 4 rounds per minute 4) In "Jutland: An Analysis of the Fighting" by John Campbell, it is stated that almost all British capital ships had few or slow hoists for their 6" (15.2 cm) guns and that once the ready ammunition was used up the rate of fire dropped to about 3 rounds per minute. This same work states that for light cruisers the rate of supply from magazines was was about three to five rounds per minute per gun and usually closer to the lower figure.

Ammunition .

Type	Bag
Projectile Types and Weights (see Notes 1 and 2)	CPBC - 100 lbs. (45.4 kg) CPC 4crh - 100 lbs. (45.4 kg) HE 4crh - 100 lbs. (45.4 kg) HE 6crh - 112 lbs. (50.8 kg)
Bursting Charge	HE (1901) - 8.7 lbs. (3.9 kg) CPC - 7.5 lbs. (3.4 kg) HE 4crh - 13.3 lbs. (6.0 kg)
Projectile Length	CPC - 23.5 in (59.7 cm) HE - 22.9 in (58.2 cm)
Propellant Charge (see Note 1)	Pre-World War I: 20 lbs. (9.1 kg) Mark I World War I: 28.6 lbs. (13 kg) MD26 Light charge: 23.1 lbs. (10.5 kg) SC103 Heavy charge: 28.2 lbs. (12.78 kg) SC140 Special charge: 28.3 lbs. (12.81 kg) SC150
Muzzle Velocity (see Notes 1, 2 and 3)	Pre-World War I: 2,536 fps (773 mps) Light charge: 2,573 fps (784 mps) Heavy charge: 2,775 fps (846 mps) Special charge: 2,640 fps (805 mps)
Working Pressure	N/A
Approximate Barrel Life	N/A
Ammunition stowage per gun	King Edward: 200 rounds Others: about 200 rounds
Notes: 1) Light and heavy charges were used only for 100 lbs. (45.4 kg) projectiles while Special charges were used only for 112 lbs. (50.8 kg) projectiles. The King Edwards class, the Iron Duke class, Tiger, the Hampshire class and Swift used the Heavy charges while all others used Light charges during World War I. Durng World War II, the gunboats Aphis, Cockchafer and Scarab used the Heavy charge. Only the AMCs Alcantara, Carnarvon Castle, Cheshire and Worcester used the 112 lbs. (50.8 kg) HE projectiles and the Special charge. 2) This gun was capable of a higher muzzle velocity, but for standardization purposes with other Marks of 6 in (15.2 cm) guns, the above values were used. This allowed all guns to use the same range tables. The Mark III rifling with the larger chamber allowed use of a slightly larger charge of 28.63 lbs. (13.0 kg) and this gave a new-gun muzzle velocity of 2,772 fps (845 mps). 3) Coastal Artillery units armed with the Mark VII* and Mark VIIv* guns used a larger charge of 29.9 lbs. (13.6 kg) SC140 giving them a muzzle velocity of 2,890 fps (881 mps) and a range at 45 degrees of 25,100 yards (22,950 m) with 6crh 100 lbs. (45.4 kg) shells, but this combination was never used on a ship.

Range .

Elevation	With 100 lbs. (45.4 kg) HE Shell
Range @ 20 degrees (see Note)	MD26 and Light charge: 14,600 yards (13,350 m) Heavy charge: 15,800 yards (14,450 m)
Elevation	With 112 lbs. (50.8 kg) HE Shell
Range @ 20 degrees	Special charge: 17,870 yards (16,340 m)
Note: During the Falklands Battle of 1914, these 6" (15.2 cm) guns on HMS Kent were reported to have been badly outranged by the much smaller German 10.5 cm (4.1") guns on SMS Nürnberg. However, the heavier British shells with their lyddite bursters were significantly more effective than the lighter German ones.

Armor Penetration with 100 lbs. (45.4 kg) CPC Projectile .

Range	KC Side Armor
3,000 yards (2,740 m)	2.0 in (5.1 cm)
Note: Data from "The Grand Fleet: Warship Design and Development 1906-1922" for an angle of obliquity of 30 degrees and a striking velocity of 1,321 fps (403 mps). Projectiles were salt-filled (blind).

Mount / Turret Data .

Designation	Single Mount King Edward (10), Challenger (11), Cressy (12), Drake (16), Monmouth (10) and Devonshire (6): PIII and PIV Insect (2): PIII Tiger (12) and Iron Duke (12): PVIII AMCs, other auxiliary warships and DEMS: PIII, PIV or PVII Twin Mount Monmouth (2): Mark I (Vickers) or Mark II (EOC)
Weight	N/A
Elevation	PIII and PIV: -7 / +15 Some later modified to +20 degrees PVIII: -7 / +14 degrees
Elevation Rate	Manual operation, only
Train	Single Mounts about -80 / +80 degrees in casemate mountings about -150 / +150 degrees in open mountings Twin Mount about -150 / +150 degrees
Train Rate	Manual operation, only
Gun recoil	N/A
Notes: 1) The twin mount was too cramped for efficient operation and suffered from electrical problems. It was also said that the weight of these turrets caused heavy pitching in bad weather. 2) Elevation of many PIII and PIV mountings was later increased to +20 degrees.

Data from
"Warrior to Dreadnought: Warship Development 1860-1905" and "The Grand Fleet: Warship Design and Development 1906-1922" both by D.K. Brown
"The Majestic Pre-Dreadnought" articles by R.A. Burt in "Warship Volume VII"
"Big Gun Monitors: The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
"Naval Weapons of World War Two" and "British Naval Guns 1880-1945 No 11" article in "Warship Volume VII" both by John Campbell
"Cruisers of the Royal and Commonwealth Navies" by Douglas Morris
"British Battleships: 1860 - 1950" by Oscar Parkes
"A Concentrated Effort: Royal Navy Gunnery Exercises at the End of the Great War" article by William Schleihauf in "Warship International" No. 2, 1998
"Graf Spee's Raiders: Challenge to the Royal Navy, 1914-1915" by Keith Yates
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Special help from Daniel Muir

Page History

27 June 2008 - Benchmark
30 January 2009 - Deleted comment regarding 45 caliber vs. 50 caliber, added additional ship information in the "Ship Class Used On" section and in the Mount / Turret "Designation" section