Britain 4"/50 (10.2 cm) BL Mark VII

Britain
4"/50 (10.2 cm) BL Mark VII
Updated 04 November 2012

This weapon entered service on the dreadnought HMS Bellerophon and later replaced many of the 4"(10.2 cm) Mark I and Mark III guns used on older Dreadnoughts.

These weapons were installed in both casemates and in single open mounts on early British dreadnoughts. The open mounts were installed without shields but some ships had these added after 1917. In 1918 a HA mounting using a reduced charge was introduced and most capital ships had one or two of these installed on a main caliber turret for anti-aircraft purposes.

During World War II these weapons were used on many minor warships and a considerable number were used as coastal artillery.

Mark VII was constructed of inner A and A tubes, wire wound, B tube to the muzzle with jacket, breech ring and breech bush screwed into the A tube. Used a Welin breech block with "pure couple" breech mechanism. Cannelured rings for reducing "steel choke" were placed between the shoulders of the A and inner A tubes. Mark VII* was a single gun made by Beardmore with a different construction. Mark VII** were fifteen guns with no inner A tube and with the B tube and jacket being combined.

Firing could be either percussion or electrical. A total of 700 of these weapons were produced, of which 482 still remained in 1939.

4"/50 (10.2 cm) BL Mark VII on unidentified DEMS circa 1943
Canada Department of National Defence / Library and Archives Canada Photograph PA-116103

HMS Vanguard
4"/50 (10.2 cm) guns in superstructure and on "X" turret, the latter were not HA mountings

HMS Thunderer showing superstructure 4"/50 (10.2 cm) guns
Photograph copyrighted by D.K. Brown

Images at Australian War Memorial

Picture of 4"/50 (10.2 cm) Mark VII gun on HMAS Australia
Search via "EN0016"

Gun Characteristics .

Designation	4"/50 (10.2 cm) BL Mark VII, VII and VIII*
Ship Class Used On	Bellerophon, St. Vincent, Neptune, Indefatigable, Colossus, Orion, Lion and King George V (1910) classes Boadicea, Active and Bristol light cruiser classes plus smaller warships Indomitable as rearmed During World War II this weapon was used mostly on DEMS
Date Of Design	About 1904
Date In Service	1908
Gun Weight	4,687 lbs. (2,126 kg)
Gun Length oa	208.5 in (5.295 m)
Bore Length	201.3 in (5.112 m)
Rifling Length	171.6 in (4.359 m)
Grooves	32
Lands	N/A
Twist	Uniform RH 1 in 30
Chamber Volume	600 in³ (9.83 dm³)
Rate Of Fire	about 6 - 8 rounds per minute

Ammunition .

Type	Bag
Projectile Types and Weights	HE - 31 lbs. (14.06 kg) CPC - 31 lbs. (14.06 kg) Shrapnel - 31 lbs. (14.06 kg)
Bursting Charge	N/A
Projectile Length	N/A
Propellant Charge	World War I: 9.37 lbs. (4.3 kg) MD16 World War I HA: 6.0 lbs. (2.7 kg) MD8 World War II: 9.7 lbs. (4.4 kg) SC103
Muzzle Velocity	2,864 fps (873 mps) With HA charge: about 2,400 fps (732 mps)
Working Pressure	N/A
Approximate Barrel Life	1,200 rounds
Ammunition stowage per gun (see Note 2)	Indomitable (as rearmed) and Indefatigable: 100 rounds Lion: 150 rounds Others: N/A
Notes: 1) Projectiles were 3crh. 2) Outfit for the Indefatigable class as commissioned and Indomitable as rearmed was 50 CPC and 50 HE, later 30 CPC and 70 HE, still later 25 CPC, 60 HE and 15 HE with night tracer. Outfit for the Lion class as commissioned was 75 CPC and 75 shrapnel. Later, she carried 160 HE and 40 Incendiary.

Range .

Elevation	With 31 lbs. (14.1 kg) HE Shell
Range @ 15 degrees	11,600 yards (10,610 m)

Mount / Turret Data .

Designation	Single Mounts PII, PII, PIV, PIV** and PVIII HA Mark II Bellerophon (16), St. Vincent (20), Neptune (16), Indefatigable (16), Orion (16), Lion (16) and King George V (16)
Weight	N/A
Elevation	PII, PII* and PVI: -7 / +15 degrees PIV, PIV* and PVIII: -10 / +15 degrees HA Mark II: -10 (?) / +60 degrees
Elevation Rate	Manually operated, only
Train	Open mounts: 360 degrees Casemate mounts: About +30 to +150 degrees
Train Rate	Manually operated, only
Gun recoil	N/A

Data from
"The Grand Fleet: Warship Design and Development 1906-1922" by D.K. Brown
"Warship Special No. 1: Battlecruisers," "Naval Weapons of World War Two" and "British Naval Guns 1880-1945 No 17" article in "Warship Volume X" all by John Campbell
"Naval Weapons of World War One" By Norman Friedman
"British Battleships 1860 - 1950" by Oscar Parkes
"Battlecruisers" by John Roberts
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The World War I Document Archive Handbook
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Special Help from Rod Butcher

Page History

14 October 2008 - Benchmark
28 January 2010 - Added picture of gun on DEMS
12 February 2012 - Updated to latest template
04 November 2012 - Added ammunition outfits for battlecruisers