6"/49 (15.2 cm) BL Mark XVIII
Updated 30 January 2009

This was originally a 15 cm/50 (5.87") gun designed by Elswick to be used as secondary weapons for the Norwegian coastal defense ships Bjöergvin and Nidaros.  These ships were under construction by Armstrongs, but at the start of World War I they were taken over by Britain and renamed HMS Glatton and HMS Gorgon.  The guns were then relined to 6" (15.2 cm) in order to use standard British ammunition.  The actual bore length after relining was 48.92 calibers.

Construction was similar to the Mark XVII, but the long jacket was replaced with a B tube and shorter jacket.  Used a hand-worked Welin breech-block.  A total of ten guns were manufactured.

Nomenclature note:  The 6"/35 (15.2 cm) Mark XIX was an Army field gun of World War I.  About 310 were manufactured by Vickers before the Armistice and it was still in service during World War II although its muzzle velocity of 2,420 fps (738 mps) was significantly lower than that of comparable field guns of the USA and Germany.


HMS Gorgon in 1918
Note the high mainmast and that it was in the path of the funnel gases
IWM (CPL) Photograph

Gun Characteristics
Designation 6"/49 (15.2 cm) BL Mark XVIII
Ship Class Used On Glatton Class monitors
Date Of Design about 1913
Date In Service 1918
Gun Weight 8.733 tons (8.873 mt)
Gun Length oa 303.93 in (7.720 m)
Bore Length 293.52 in (7.455 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume 1,650 in3 (27.04 dm3)
Rate Of Fire 3 rounds per minute
Type Bag
Projectile Types and Weights CPC 4crh - 100 lbs. (45.3 kg)
HE 4crh - 100 lbs. (45.3 kg)
Bursting Charge CPC - 7.5 lbs. (3.4 kg)
HE - 13.3 lbs. (6.0 kg)
Projectile Length CPC - 23.5 in (59.7 cm)
HE - 22.9 in (58.2 cm)
Propellant Charge 28.63 lbs. (12.99 kg) MD26
Muzzle Velocity 2,874 fps (876 mps)
Working Pressure N/A
Approximate Barrel Life 1,200 rounds
Ammunition stowage per gun 200 rounds
Note:  Outfit was 100 CPC and 100 HE per gun.
Elevation With 100 lbs. (45.36) HE Shell
Range @ 20 degrees 16,020 yards (14,650 m)
Mount / Turret Data
Designation Single Mounts
   Glatton (4):  Mark IV
Weight (less shield) 65.7 tons (66.8 mt)
Elevation -5 / +20 degrees
Elevation Rate N/A
Train Bow and stern:  about -150 / +150 degrees
Amidships:  about -80 / +80 degrees
Train Rate N/A
Gun recoil N/A
Data from
"Big Gun Monitors:  The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
"British Naval Guns 1880-1945 No 12" article in "Warship Volume VIII" by John Campbell
Page History

21 July 2006 - Benchmark
30 January 2009 - Added construction details