The Mark VIII was introduced on the "Special Flotilla Leader Destroyer" Swift and subsequently used on many pre-World War I destroyers. Some guns were modified for HA use during World War I.
Following the war, four guns were sent to the Caspian in 1919. During World War II, many guns were used to arm DAMS merchantmen.
The Mark XI was the Mark VIII adapted for submarine use.
The Mark VIII was constructed of A tube, breech piece, B tube to the muzzle, wire over the breech piece, jacket, breech ring and bush screwed into the breech piece. Used a Welin block with a "pure couple" breech mechanism. Later guns and the Mark XI had a tapered inner A and A tube instead of the A tube, B tube and Breech piece. Firing could be via either percussion or electrical means. Actual bore length of all guns was 39.8 calibers. When worn, the guns were repaired by boring out a part of the A tube and inserting a tapered liner.
A total of 246 of the Mark VIII guns were produced, of which 194 still remained in 1939. Thirty Mark XI guns were manufactured, all of which were apparently scrapped by 1939.
|Designation||4"/40 (10.2 cm) BL Mark VIII 4"/40 (10.2 cm) BL Mark XI|
|Ship Class Used On 1||Mark VIII
Destroyers 2: Swift, later Tribals starting with Saracen, first 13 members of the K class, Acasta class members Acasta, Midge and Spitfire
Submarines: E2, E11, E12, E14, E21 and E25
"Fly" class river gunboats
Some P ships and Q ships
Australian Swan class
|Date Of Design||About 1904|
|Date In Service||1908|
|Gun Weight||1.296 tons (1,317 kg)|
|Gun Length oa||166.4 in (4.227 m)|
|Bore Length||159.2 in (4.044 m)|
|Twist||Uniform RH 1 in 30|
|Chamber Volume||298 in3 (4.88 dm3)|
|Rate Of Fire||About 6 - 8 rounds per minute|
|Projectile Types and Weights 1a||HE: 31 lbs. (14.06 kg)
CPC: 31 lbs. (14.06 kg)
Shrapnel: 31 lbs. (14.06 kg)
|Propellant Charge||World War I: 5.38 lbs. (2.4 kg) MD16
World War II: 5.5 lbs. (2.5 kg) SC103
|Muzzle Velocity||2,287 fps (697 mps)|
|Approximate Barrel Life||N/A|
|Ammunition stowage per gun||N/A|
- ^Projectiles were 3crh.
|20 degrees||10,210 yards (9,340 m)|
|Designation||Mark VIII (LA) Guns
Swift (4), Tribals (2) and K (3): CPIII, CPIII*, CPV and CPVII
Mark VIII (HA) Guns 1b
Mark XI (Submarine) Guns
|Elevation||All except HA conversions: -10 / +20 degrees
HA conversions: N/A, but probably about -10 / +70 degrees
|Elevation Rate||Manually operated, only|
|Train||CP type: 360 degrees
SI: About -120 / +120 degrees
|Train Rate||Manually operated, only|
- ^HA mountings had a "trap door" gun pit which allowed higher elevations by letting the breech go below the mounting deck level. These guns were carried on a few K class destroyers and on the Acasta class destroyers Acasta, Midge and Spitfire (one gun).
"Warrior to Dreadnought: Warship Development 1860-1905" and "The Grand Fleet: Warship Design and Development 1906-1922" both by D.K. Brown
"Naval Weapons of World War Two" and "British Naval Guns 1880-1945 No 17" article in "Warship Volume X" both by John Campbell
The World War I Document Archive
16 October 2008 - Benchmark
30 January 2009 - Updated HMS Swift picture caption to include link, added information in the Mount / Turret "Designation" section
29 February 2012 - Added mounting information
16 June 2012 - Added picture of HMAS Warrego
29 November 2022 - Converted to HTML 5 format