12"/46 (30.5 cm) Model 1909
Updated 26 May 2012

These were of two types, Elswick Pattern "T" and Vickers Mark "G".  Elswick guns armed the Dante class while Vickers armed the Doria class.  The guns for Cavour were manufactured in Italy by Vickers-Terni while those of Leonardo da Vinci were built by Armstrongs in Britain and those of Cesare were manufactured by the Italian branch of Armstrongs at Pozzuoli in Naples.  The mountings were all hydraulically operated.

The delivery of these weapons was greatly delayed, the average being over one year later than planned.  For Cavour, this delay would have been even longer, but guns intended for Doria were used when her construction was delayed.

In the 1930s many of these guns were bored out to 32 cm (12.6") for the reconstructed Cesare and Duilio class battleships, but some were retained in their original caliber and used in coastal artillery batteries.

Mark "G" was a fully wire-wound type with inner A, A, B tubes, jacket and breech ring.  Pattern "T" had an inner A tube, A tube in two parts joined by screwed collar, B tube and half-length wire, jacket and short breech ring.  A pneumatically operated Welin breech block was used for both.


Battleship Dante Alighieri
This was the first ship to carry large caliber guns in triple turrets
Note the arrangement of funnels
Photograph by Malandrini Ferrucclo, Alinari Archives-Florence

Click here for additional pictures
Gun Characteristics
Designation 12"/46 (30.5 cm) Model 1909
Ship Class Used On Dante Alighieri, Conte di Cavour and Caio Duilio Classes
Date Of Design 1909
Date In Service 1913
Gun Weight 62.5 tons (63.5 mt)
Gun Length oa about 571 in (14.500 m)
Bore Length 552.0 in (14.021 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire 2 rounds per minute
Type Bag
Projectile Types and Weights APC - 997 lbs. (452 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge N/A
Muzzle Velocity 2,758 fps (840 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun
(see Note)
Dante Alighieri:  N/A
Conte di Cavour and Caio Duilio:  100 rounds
Note:  Normal outfit for Conte di Cavour and Caio Duilio was 40 rounds AP and 30 rounds HE fragmentation shells but there was space for 100 rounds.
Elevation With 997 lbs. (452 kg) AP shell
Range @ 20 degrees 26,240 yards (24,000 m)
Mount / Turret Data
Designation Two-gun Turrets
  Conte di Cavour (2) and Caio Duilio (2)

Three-gun Turrets
  Dante Alighieri (4), Conte di Cavour (3) and Caio Duilio (3)

Weight  Two-gun Turrets
   about 500 tons (508 mt)

Three-gun Turrets
   Dante Alighieri class:  645 tons (655 mt)
   Conte di Cavour and Caio Duilio classes:  670 tons (681 mt)

Elevation -5 / +20 degrees
Elevation Rate N/A
(see Note 1)
Conte di Cavour class
   A and X turrets:  +150 / -150 degrees
   B and Y turrets:  +155 / -155 degrees
   Q turret:  360 degrees

Caio Duilio class
   A and X turrets:  +143 / -143 degrees
   B turret:  +153 / -153 degrees
   Q turret:  360 degreees
   Y turret:  +155 / -155 degrees

Train Rate N/A
Gun recoil N/A
Loading Angle Any angle

1) Please note that although Q turret on these ships could train a full 360 degrees, it could not fire directly forward or aft without striking the superstructure of the ship.

2) Ammunition supply was hydraulically powered while the elevation machinery was an electrical-hydraulic system.

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"
"The Big Gun:  Battleship Main Armament 1860-1945" by Peter Hodges
"Battleships of World War I" by Peter Hore
Marina Militare Press Releases
Page History

02 May 2008 - Benchmark
26 May 2012 - Added mounting notes