Description

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 ODO. 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.

Gun Characteristics

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

Ammunition

Type Bag
Projectile Types and Weights AP: 1,157 lbs. (525 kg)
HE: 1,010 lbs. (458 kg)
Bursting Charge N/A
Projectile Length N/A (probably 4.46 calibers)
Propellant Charge 386 lbs. (175 kg) 1
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

The Naval Museum in Venice, Italy, has a 320 mm APC projectile on display (Inventory #4402).

  • ^Propellant charges were in quarters.

Range

Range with 1,157 lbs. (525 kg) AP
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)

Mount/Turret Data

Designation
  • Two-gun Turrets
    • Cavour (2): Model 1934
    • Duilio (2): Model 1936
  • Three-gun Turrets
    • Cavour (2): Model 1934
    • Duilio (2): Model 1936
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.

Sources

Data from:

  • "Regia Marina: Italian Battleships of World War Two" by Erminio Bagnasco and Mark Grossman
  • "Naval Weapons of World War Two" by John Campbell
  • "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

Special help by Nathan Okun

Sources

03 November 2008
Benchmark
26 May 2012
Updated to latest template