British
4"/40 (10.2 cm) BL Mark VIII and Mark XI
Updated 16 October 2008
The Mark VIII was introduced on the "Special Flotilla Leader Destroyer" Swift and used on many subsequent pre-World War I destroyers.  Some Mark VIII 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 IX guns were manufactured, all of which were apparently scrapped by 1939.
WNBR_4-40_mk8_Swift_pic.jpg

HMS Swift
The paired 4" (10.2 cm) guns on the bow were later replaced with a single 6" (15.2 cm) gun, type unknown
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Gun Characteristics
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Designation 4"/40 (10.2 cm) BL Mark VIII and Mark XI
Ship Class Used On
(see Note 1)		 Mark VIII
   Destroyers:  Swift, Tribals, K class
   Submarines:  E2, E11, E12, E14, E21 and E25
   "Fly" class river gunboats
   Some P ships and Q ships
   Australian Swan class

Mark XI
   Submarines:  J1, K1-4, K6-16
   Some Q ships
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)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist Uniform RH 1 in 30
Chamber Volume 298 in3 (4.88 dm3)
Rate Of Fire About 6 - 8 rounds per minute
Notes:

1) The Japanese destroyer Sakaki carried one of these guns in 1918.  This may have been installed when she was rebuilt after being torpedoed by the Austrian submarine U.27 in 1917.

2) Modified HA guns were used on the K class destroyers, Acasta, Midge and Spitfire (one gun).
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Ammunition
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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:  5.38 lbs. (2.4 kg) MD16
World War II:  5.5 lbs. (2.5 kg) SC103
Muzzle Velocity 2,287 fps (697 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A
Note:  Projectiles were 3crh.
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Range
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Elevation With 31 lbs. (14.1 kg) HE Shell
Range @ 20 degrees 10,210 yards (9,340 m)
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Mount / Turret Data
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Designation Single Mounts
   For the Mark VIII:  CPIII, CPIII*, CPV and CPVII
   For the Mark XI:  SI
Weight  N/A
Elevation All except HA conversions:  -10 / +20 degrees
HA conversions:  N/A
Elevation Rate Manually operated, only
Train CP type:  360 degrees
SI:  About -120 / +120 degrees
Train Rate Manually operated, only
Gun recoil N/A
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Data from
"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
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The World War I Document Archive