This weapon was specifically developed for the submarine X 1, which was the British version of the "submarine cruiser." These were submarines with large-caliber armament built by Germany during World War I and by other nations during the 1920s. None of these boats were very successful.

For the X 1, the design concept was that she should be able sink or disable a destroyer at 6,000 yards (5,500 m) with her guns alone. In practice, this was unlikely, as the low height above the water of the range finding equipment and the unsteady nature of a submarine made this craft unsuitable as a gun platform. This was the only gun of this caliber built by the British and was considered to be reliable once the initial problems had been overcome.

Consisted of tapered inner A tube, A tube, partial jacket, and breech ring. Used a horizontal sliding, hand operated breech block with semi-automatic opening. A total of six guns were built.

Gun Characteristics

Designation 5.2"/42 (13.2 cm) QF Mark I
Ship Class Used On X 1
Date Of Design About 1921
Date In Service 1924
Gun Weight 3.425 tons (3.48 mt)
Gun Length oa 230.65 in (5.859 m)
Bore Length 218.4 in (5.547 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume 630 in3 (10.32 dm3)
Rate Of Fire 6 rounds per minute


Type Separate
Projectile Types and Weights HE: 70 lbs. (31.8 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 10.78 lbs. (4.9 kg) MC 16
11.36 lbs. (5.2 kg) SC 109
Muzzle Velocity 2,300 fps (701 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun 100 rounds


Range with 70 lbs. (31.8 kg) HE
Elevation Distance
40 degrees 17,288 yards (15,800 m)

Mount/Turret Data

  • Twin open mount
    • X 1 (2): Mark I
Weight N/A
Elevation -5 / +40 degrees
Elevation Rate Manually operated, only
Train about -150 / +150 degrees
Train Rate Manually operated, only
Gun recoil N/A

Special ballast tanks were fitted which compensated for the loss of weight as the ammunition was fired.

Gunnery crew was 58 out of a total complement of 109.


Data from:

  • "The Grand Fleet: Warship Design and Development 1906-1922" and "X1 - Cruiser Submarine" article in "Warship Volume VI" both by D.K. Brown
  • "British Naval Guns 1880-1945 No 14" article by John Campbell in "Warship Volume VIII"

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