These were originally 12"/46 (30.5 cm) Model 1909 guns used on battleships built before and during World War I. In the 1930s, these guns were rebuilt as part of the massive reconstruction of the old battleships. The conversion was judged to be satisfactory with 13.4% more muzzle energy being obtained. However, the rebuilt guns had more longitudinal droop and slightly more shell dispersion.
The Cesare class guns were of Elswick Pattern "T" and those of the Duilio class were of Vickers Mark "G" type. Welin breech-blocks were used for both types. The Elswick guns were converted by Ansaldo and the Vickers guns by OTO. See the 12"/46 (30.5 cm) Model 1909 data page for the original construction details. The conversion consisted of boring out to remove the original A tube and apparently some of the wire. The remainder was shrunk on to a new A tube. It is possible that a shrunk or tupped inner A tube was also fitted.
Actual bore length of these reworked guns was 43.75 calibers.
| Designation | 320 mm/44 (12.6") Model 1934 and Model 1936 |
|---|---|
| Ship Class Used On | OTO Model 1934: Cavour Class
Ansaldo Model 1936: Doria Class |
| Date Of Design | 1934 and 1936 (as remanufactured) |
| Date In Service | 1940 (as remanufactured) |
| Gun Weight | 64 tons (69,672 kg) |
| Gun Length oa | about 571 in (14.500 m) |
| Bore Length | 551.2 in (14.000 m) |
| Rifling Length | about 446 in (11.320 m) |
| Grooves | about 80 |
| Lands | N/A |
| Twist | Uniform RH 1 in 30 |
| Chamber Volume | about 21,360 in3 (450 dm3) |
| Rate Of Fire | 2 rounds per minute |
| Type | Bag |
|---|---|
| Projectile Types and Weights 1 | APC: 1,157 lbs. (525 kg)
SAPBC: 1,010 lbs. (458 kg) |
| Bursting Charge | APC: 14.1 lbs. (6.38 kg) Cast TNT
SAPBC: 51.6 lbs. (23.40 kg) Cast TNT |
| Projectile Length | N/A (probably 4.46 calibers) |
| Propellant Charge | 386 lbs. (175 kg) 2 |
| Muzzle Velocity | 2,723 fps (830 mps) |
| Working Pressure | 19.5 tons/in2 (3,100 kg/cm2) |
| Approximate Barrel Life | 150 rounds |
| Ammunition stowage per gun | 100 rounds |
| Elevation | Distance |
|---|---|
| 27 degrees
(max elevation of Cavour) |
31,280 yards (28,600 m) |
| 30 degrees
(max elevation of Doria) |
32,150 yards (29,400 m) 1a |
- ^This range is taken from "Italian Warships of World War II." "Naval Weapons of World War Two" believes that this range is an error and the actual range would be closer to 33,100 yards (30,270 m).
| Range | Angle of Obliquity (Degrees) 2b | ||||
|---|---|---|---|---|---|
| 90 | 80 | 70 | 60 | 50 | |
| 24,000 m (26,250 yards) | 221 mm (8.70 in) | 216 mm (8.50 in) | 202 mm (7.95 in) | 179 mm (7.05 in) | 150 mm (5.91 in) |
| 22,000 m (24,060 yards) | 238 mm (9.37 in) | 232 mm (9.13 in) | 218 mm (8.58 in) | 194 mm (7.64 in) | 162 mm (6.38 in) |
| 20,000 m (21,870 yards) | 256 mm (10.08 in) | 249 mm (9.80 in) | 235 mm (9.25 in) | 209 mm (8.23 in) | 174 mm (6.85 in) |
| 18,000 m (19,690 yards) | 276 mm (10.87 in) | 270 mm (10.63 in) | 254 mm (10.00 in) | 225 mm (8.86 in) | 189 mm (7.44 in) |
| Range | Angle of Obliquity (Degrees) 2b | ||||
|---|---|---|---|---|---|
| 90 | 80 | 70 | 60 | 50 | |
| 24,000 m (26,250 yards) | 150 mm (5.91 in) | 150 mm (5.91 in) | 150 mm (5.91 in) | 148 mm (5.83 in) | 124 mm (4.88 in) |
| 22,000 m (24,060 yards) | 150 mm (5.91 in) | 150 mm (5.91 in) | 150 mm (5.91 in) | 150 mm (5.91 in) | 135 mm (5.31 in) |
| 20,000 m (21,870 yards) | 152 mm (5.98 in) | 150 mm (5.91 in) | 150 mm (5.91 in) | 150 mm (5.91 in) | 140 mm (5.51 in) |
| 18,000 m (19,690 yards) | 162 mm (6.38 in) | 152 mm (5.98 in) | 150 mm (5.91 in) | 150 mm (5.91 in) | 142 mm (5.59 in) |
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 | 24,000 m (26,250 yards) | 108 mm (4.25 in) |
| X2 | 22,000 m (24,060 yards) | 91 mm (3.58 in) |
| X3 | 18 - 20,000 m (19,690 - 21,870 yards) | 61 - 75 mm (2.40 - 2.95 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 | Two-gun Turrets
Cavour (2): Model 1934 Duilio (2): Model 1936 Three-gun Turrets
|
|---|---|
| Weight | Two-gun Turrets: 539 tons (548 mt)
Three-gun Turrets: 733 tons (745 mt) |
| Elevation | As originally built: -5 / +20 degrees
As modernized: Cavour: -5 / +27 degrees Doria: -5 / +30 degrees |
| Elevation Rate | 6 degrees per second |
| Train | about +120 / -120 degrees |
| Train Rate | 5 degrees per second |
| Gun recoil | 41 in (1.05 m) |
| Loading Angle | +12 degrees |
- These turrets were originally hydraulically powered, but when modified were converted to electrical power.
- The gun axes were 90 in (228.6 cm) apart in both the two-gun and the three-gun mountings.
"Regia Marina: Italian Battleships of World War Two" by Erminio Bagnasco and Mark Grossman
"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
"The Cavour and Duilio Class Battleships" article by Giorgio Giorgerini in "Warship Volume IV"
"Battleships of World War I" by Peter Hore
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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 by Nathan Okun and Byron Angel
03 November 2008 - Benchmark
6 May 2012 - Updated to latest template
29 July 2019 - Updated to HTML 5 format, reorganized notes, corrected typographical error
03 April 2020 - Added note to range table
01 April 2021 - Added photograph of Andrea Doria post-war
24 October 2022 - Corrected HTML problem
16 August 2025 - Added Armor Penetration section