These guns were all manufactured by Bofors and used by the Netherlands Navy on cruisers and sloops (gunboats) built during the 1920s. It is not clear what were the differences between these different Mark numbers, although I suspect that it had to do with the mountings. All of these guns used horizontal sliding breech-blocks and had similar ballistics. Surviving ships were supplied with British-built munitions during World War II. The sloops Flores and Soemba were intensively used during the invasions of Italy and had their worn-out guns replaced with ones removed from the cruiser Sumatra.

Actual bore diameter was 14.91 cm (5.87").

Gun Characteristics

Designation 15 cm/50 (5.9") Marks 6, 7 and 8
Ship Class Used On Mark 6: Java class
Mark 7: Flores class
Mark 8: Johan Maurits van Nassau
Date Of Design 1924
Date In Service 1925
Gun Weight 7.13 tons (7.24 mt)
Gun Length oa about 310.8 in (7.895 m)
Bore Length about 293.5 in (7.455 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire 5 rounds per minute


Type Separate
Projectile Types and Weights AP: 103 lbs. (46.7 kg)
HE: 101.4 lbs. (46.0 kg)
British AP: 99.8 lbs. (45.3 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge Dutch charges: 36.8 lbs. (16.7 kg)
Cartridge: 57.7 lbs. (26.2 kg)
British charges: 35 lbs. (15.9 kg)
Muzzle Velocity AP: 2,953 fps (900 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A


Range with 103 lbs. (46.7 kg) AP
Elevation Distance
29 degrees 23,200 yards (21,214 m)

Mount/Turret Data

  • Single, open-back mounts
    • Java (10) and Sloops (3)
Weight 20.0 tons (20.35 mt)
Elevation -10 / +29 or +30 degrees
Elevation Rate N/A
Train about +150 / -150 degrees
Train Rate N/A
Gun recoil N/A

Additional Pictures


Data from:

  • "Naval Weapons of World War Two" by John Campbell
  • "Cruisers of World War Two" by M.J. Whitley
  • "Warship Pictorial: The Royal Netherlands Navy 1945-86" article in "Warships Volume X"

Page History

03 December 2008
16 June 2012
Redid picture of RNN Java and added picture of Flores