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").
| 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 a 45 degree elevation while the higher figure is for firing at or near the loading angle.
| Type | Bag |
|---|---|
| Projectile Types and Weights 1a | SAP (1924): 276.2 lbs. (125.3 kg)
SAP (later issue): 261.2 lbs. (118.5 kg) HE: 243.77 lbs. (110.57 kg) |
| Bursting Charge | SAP (1924): 6.96 lbs. (3.157 kg)
SAP (later issue): 7.5 lbs. (3.4 kg) HE: 16.5 lbs. (7.5 kg) |
| Projectile Length | SAP (1924): N/A
SAP (later issue): 33.36 in (84.7 cm) Others: N/A |
| Propellant Charge | 104.3 lbs. (47.3 kg) 2a |
| Muzzle Velocity 3a | SAP (later issue): 2,756 fps (840 mps)
HE: N/A |
| Working Pressure | 17.8 tons/in2 (2,800 kg/cm2) |
| Approximate Barrel Life | N/A |
| Ammunition stowage per gun | 216 rounds 4a |
- ^
Actual Italian designations SAP (1924) Granata Perforanti [Armor Piercing Grenade] da 203/50 SAP (later issue) Granata Perforanti [Armor Piercing Grenade] da 203/50 HE Granata Dirompente (Disruptive Grenade) da 203/50 - ^The propellant weight given here is for the lower MV of 2,756 fps (840 mps).
- ^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.
- ^Magazines held a total of 1,300 projectiles and 2,900 half-charges.
| Range | Angle of Obliquity (Degrees) 2c | ||||
|---|---|---|---|---|---|
| 90 | 80 | 70 | 60 | 50 | |
| 22,000 m (24,060 yards) | * | * | * | * | * |
| 20,000 m (21,870 yards) | 100 mm (3.93 in) | * | * | * | * |
| 18,000 m (19,690 yards) | 117 mm (4.61 in) | 115 mm (4.53 in) | 107 mm (4.21 in) | * | * |
| 16,000 m (17,500 yards) | 137 mm (5.39 in) | 135 mm (5.31 in) | 127 mm (5.00 in) | 112 mm (4.41 in) | * |
* = Does not penetrate the minimum thicknesses [100 mm (3.9 in)].
| Range | Angle of Obliquity (Degrees) 2c | ||||
|---|---|---|---|---|---|
| 90 | 80 | 70 | 60 | 50 | |
| 22,000 m (24,060 yards) | 96 mm (3.78 in) | 94 mm (3.70 in) | 88 mm (3.46 in) | 79 mm (3.11 in) | ** |
| 20,000 m (21,870 yards) | 109 mm (4.29 in) | 107 mm (4.21 in) | 100 mm (3.94 in) | 89 mm (3.50 in) | 74 mm (2.91 in) |
| 18,000 m (19,690 yards) | 127 mm (5.00 in) | 123 mm (4.84 in) | 116 mm (4.57 in) | 100 mm (3.94 in) | 87 mm (3.43 in) |
| 16,000 m (17,500 yards) | 150 mm (5.91 in) | 146 mm (5.75 in) | 137 mm (5.39 in) | 121 mm (4.76 in) | 102 mm (4.02 in) |
** = Does not penetrate the minimum thicknesses (minimum thickness not specified).
Maximum Ranges at which given Thicknesses of Horizontal Armor (Homogeneous) can be Penetrated
X1 = Penetration @ maximum range of opening of fire under conditions of exceptional visibility.
X2 = Penetration @ maximum range of opening of fire under conditions of normal visibility.
X3 = Penetration @ typical combat range band, once engaged.
| X Number | Range | Armor Penetration |
|---|---|---|
| X1 | 22,000 m (24,060 yards) | 43 mm (1.69 in) |
| X2 | 20,000 m (21,870 yards) | 91 mm (1.54 in) |
| X3 | 16 - 18,000 m (17,500 - 19,690 yards) | 25 - 31 mm (0.98 - 1.22 in) |
Data in this table taken from a memorandum of 10 December 1939 by the Commissione Permanente per gli Esperimenti del Materiale di Guerra (Mariperman) [Permanent Commission for the Experiments of the Material of War (Mariperman)].
| Designation | Twin Turrets
Trento (4): Model 1924 |
|---|---|
| Weight | N/A |
| Elevation | -7 / +45 degrees |
| Elevation Rate | N/A |
| Train | +150 / -150 degrees |
| Train Rate | N/A |
| Gun recoil | 27.5 in (70 cm) |
| Loading Angle | +15 degrees |
- Guns were in a common cradle and gun axes were 39.4 inches (100 cm) apart. Mountings used electric power for training, elevation, hoists and rammers. Shell hoists were pusher type and there was only one hoist per turret which ran directly up to the gunhouse. Magazines were below the shell rooms.
"Italian Heavy Cruisers: From Tento to Bolzano" by Maurizio Brescia and Augusto de Toro
"Naval Weapons of World War Two" by John Campbell
"Questioni Di Tiro: E Altre le Artiglierie Navali Italiane Nella Guerra Nel Mediterraneo"
[Questions of Fire: And Others for the Italian Naval Artillery in the War in the Mediterranean] by Giuliano Colliva
"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
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Memorandum of the Commissione Permanente per gli Esperimenti del Materiale di Guerra (Mariperman)
[Permanent Commission for Experiments of War Material (Mariperman)], 111/RP of 10 December 1939, "Dati circa gli effetti dei proietti su
bersaglio navale", diretto a Maristat [Data on the Effects of Projectiles on Naval Targets, addressed to Maristat]. Archive of the
Historical Office of the Navy [AUSMM], Artillery and Munitions Inspectorate fund [IAM], box 2, file 3, pages 7 and 8.
"Direttive e norme per l'impiego della Squadra Navale" [Directives and regulations for the use of the Navy]
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Special help from Byron Angel
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
07 January 2025 - Added data on mountings
15 August 2025 - Added Vertical and Horizontal Armor Penetration sections