Used on the Trento (1st Group) class heavy cruisers. These guns suffered from dispersion problems, mainly because the guns were mounted so close together. The muzzle velocity and shell weights were reduced in an attempt to rectify the problems, with only partial success.

The turrets used electrical power for training, elevation, hoists and rammers. The guns were not individually sleeved. One spare turret was later used for coastal defense.

These guns were of built-up construction with a fixed liner, autofretted and used a Welin breech-block.

Actual bore diameter was 20.32 cm (8.0").

Gun Characteristics

Designation 203 mm/50 (8") Model 1924
Ship Class Used On Trento Class
Date Of Design 1924
Date In Service 1928
Gun Weight 26.66 tons (29,023 kg)
Gun Length oa 414.8 in (10.537 m)
Bore Length 400.0 in (10.160 m)
Rifling Length 334.8 in (8.505 m)
Grooves 52
Lands N/A
Twist Uniform RH 1 in 30
Chamber Volume 4,579 in3 (75.03 dm3)
Rate Of Fire 1.5 - 3.4 rounds per minute 1
  • ^The lower ROF figure is for guns fired at 45 degree elevation while the higher figure is for firing at or near the loading angle.


Type Bag
Projectile Types and Weights AP (1924): 276.2 lbs. (125.3 kg)
HE: 243.77 lbs. (110.57 kg)
AP (later issue): 260 lbs. (118 kg)
Bursting Charge AP (later issue): 7.5 lbs. (3.4 kg)
HE: 18.0 lbs. (8.2 kg)
Projectile Length AP (later issue): 33.36 in (84.7 cm)
Propellant Charge 104.3 lbs. (47.3 kg) 1a
Muzzle Velocity 2a AP (later issue): 2,756 fps (840 mps)
Working Pressure 17.8 tons/in2 (2,800 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun 216 rounds
  • ^The propellant seems to have been in a single bag.
  • ^These guns as designed had a muzzle velocity of 2,969 fps (905 mps) for the 1924 AP projectiles and 3,084 fps (940 mps) for HE projectiles. The muzzle velocity was reduced to 2,756 fps (840 mps) and the weight of the AP shells lowered in a not entirely successful attempt to reduce shell dispersion.


Range with various shells
Elevation 276.2 lbs. (125.3 kg) AP (original) 260 lbs. (118 kg) AP (WWII) 243.77 lbs. (110.57 kg) HE (WWII)
45 degrees 34,256 yards (32,324 m) 1b 30,620 yards (28,000 m) 33,410 yards (30,550 m)
  • ^This figure is with a velocity of 2,953 fps (900 mps).

Mount/Turret Data

Designation Twin Turrets
   Trento (4): Model 1924
Weight N/A
Elevation -1.5 / +45 degrees
(possibly -7 degrees)
Elevation Rate N/A
Train about +150 / -150 degrees
Train Rate N/A
Gun recoil 27.5 in (70 cm)
Loading Angle +15 degrees


"Naval Weapons of World War Two" by John Campbell
"Italian Warships of World War II" by Aldo Fraccaroli
"Warship Pictorial #23: Italian Heavy Cruisers of World War II" by Gordon E. Hogg and Steve Wiper
"Cruisers of World War Two" by M.J. Whitley

Page History

08 July 2007 - Benchmark
26 May 2012 - Updated to latest template
19 March 2020 - Updated to HTML 5 format, reorganized notes
18 January 2022 - Added photograph of Trento