These were coast defense guns developed by the Army for use against German Schnellboots ("E-boats") and other small craft. The first prototypes were under test by 1928 and series production began in 1934. Twenty-two of them were transferred to the Navy and used on old destroyers detailed for coastal escort duties.

Constructed of A tube, part length jacket and breech ring. Used a semi-automatic sliding breech block. Guns were unusual in that the gun layers did not fire the weapons. Instead, the loader for each gun actuated a firing lever after the round was loaded.

"As a measure of the firepower of the Twin 6-pounder, a battery of them at the mouth of Valetta harbour sank five Italian torpedo boats and human torpedo attack vessels in less than two minutes on the night of 25/26th July 1941." - Terry Gander.

Constructed of A tube, part length jacket and breech ring. Used a semi-automatic sliding breech block.

Gun Characteristics

Designation 6-pdr / 10cwt QF Mark I
Ship Class Used On Destroyers Campbell, Mackay, Montrose, Whitshed, Wivern, Worcester, Walpole and Windsor
Date Of Design N/A
Date In Service 1941 in naval service
Gun Weight 1,060 lbs. (481 kg)
Gun Length oa 109.72 in (2.787 m)
Bore Length 105.47 in (2.679 m)
Rifling Length 86.55 in (2.198 m)
Grooves (24) 0.012 in deep x 0.220 in (0.30 mm x 5.59 mm)
Lands 0.074 in (1.9 mm)
Twist Polygroove, plain section
Uniform RH 1 in 30
Chamber Volume 73.5 in3 (1.2 dm3)
Rate Of Fire 18 rounds per minute 1
  • ^Well-trained crews could achieve a ROF as high as 40 RPM from each barrel.


Type Fixed
Weight of Complete Round N/A
Projectile Types and Weights HE: 6.28 lbs. (2.85 kg)
HE-T: 6.54 lbs. (2.97 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 1.27 lbs. (0.576 kg) N 045
Muzzle Velocity HE: 2,386 fps (727 mps)
HE-T: 2,356 fps (718 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun 1a N/A 2a
  • ^Outfits were half HE and half HE-T (tracer).
  • ^Ready-use trays mounted behind each gun held about 20 rounds each.


Range during World War I with 6.28 lbs. (2.85 kg) HE
Elevation Distance
45 degrees 11,300 yards (10,330 m)

Mount/Turret Data

Designation Twin Mounts
   Coastal Defense: Mark I
   Destroyers (1): Mark I* 1b
Weight N/A
Elevation -10 / +80 degrees
Elevation Rate Manually operated, only
Train 360 degrees
Train Rate Manually operated, only
Gun recoil 12 in (30.5 cm)
  • ^The naval mounting had a more extensive shield than did the coast defense mounting.

Additional Pictures


"Naval Weapons of World War Two" by John Campbell
"Warships of World War II" by H.T. Lenton and J.J. Colledge
"Twentieth Century British Coast Defence Guns" by Terry Gander
Special help from Dave Alton and Richard Worth

Other Resources

Page History

16 October 2005 - Benchmark
12 February 2012 - Updated to latest template
15 December 2013 - Added photographs of HMS Mackay
03 May 2019 - Converted to HTML 5 format, reorganized notes and added to description and gun data and added Front View photograph