During World War I, these guns were used to arm the Iron Duke and Tiger classes along with 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.
Berwick in 1905
|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
During World War II:
Iron Duke, Insect class gunboats, AMCs, armed liners and DEMS
|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)|
(see Note 1)
(see Note 2)
|1,715 in3 (28.10 dm3)|
|Rate Of Fire
(see Notes 3 and 4)
|5 - 7 rounds per minute|
1) There were two different kinds of rifling in general use, designated as Mark I and Mark III. The Mark III rifling allowed a larger chamber but I have been unable to determine the other 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
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.
|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)
(see Note 1)
|Pre-World War I: 20 lbs. (9.1 kg)
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
(see Notes 1, 2 and 3)
|Pre-World War I: 2,536 fps (773
Light charge: 2,573 fps (784 mps)
Heavy charge: 2,775 fps (846 mps)
Special charge: 2,640 fps (805 mps)
|Approximate Barrel Life||N/A|
|Ammunition stowage per gun||King Edward: 200 rounds
Iron Duke: 130 rounds
Tiger: 120 rounds
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 all used the Heavy charges while the other ships used Light charges during World War I. During 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.
|Elevation||With 100 lbs. (45.4 kg) HE Shell|
|Range @ 20 degrees
|MD26 and Light charge: 14,600 yards
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 the cruiser Nürnberg. However, the heavier British shells with their lyddite bursters were significantly more effective than the lighter German ones.|
|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).|
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
|Elevation||PIII and PIV: -7 / +15
Some later modified to +20 degrees
PVIII: -7 / +14 degrees
|Elevation Rate||Manual operation, only|
about -80 / +80 degrees in casemate mountings
about -150 / +150 degrees in open mountings
|Train Rate||Manual operation, only|
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.
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
05 January 2014 - Added additional pictures datapage
02 February 2014 - Added ammunition stowage for Iron Duke and Tiger
23 November 2014 - Added pdf Range Table