The 320 mm naval gun was the main battery gun used to modernize Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

's World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 battleship

Battleship

A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...

s for service during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. The guns were manufactured by boring out and relining the battleships' original 12"/50 (30 cm) built-up gun

Built-up gun

The term built-up gun describes a construction technique for artillery barrels. An inner tube of metal which stretches most within its elastic limit enlarges under the pressure of confined powder gases to transmit stress to outer cylinders under tension...

s and modifying the turrets to increase elevation above the original 20°  maximum. Each ship carried two 548-tonne twin turrets and two 745-tonne triple turrets. All guns used pneumatically operated side-swing Welin breech block

Welin breech block

The Welin breech block was a revolutionary stepped, interrupted thread design for locking artillery breeches, invented by Axel Welin in 1889 or 1890...

s. Each barrel could fire two rounds per minute.

M1934 guns

Conte di Cavour class battleships

Conte di Cavour class battleship

The Conte di Cavour class was a battleship class of the Regia Marina in World War I and World War II.-Design:This class was the second group of dreadnoughts in the Regia Marina. The ships were designed by Admiral Edoardo Masdea....

 Conte di Cavour

Italian battleship Conte di Cavour

Conte di Cavour was an Conte di Cavour class battleship, that served in the Regia Marina during World War I and World War II. It was named after the Italian statesman Count Camillo Benso di Cavour.-Construction and first years:...

 and Giulio Cesare

Italian battleship Giulio Cesare

Giulio Cesare , motto Caesar Adest was a Conte di Cavour-class battleship that served in the Regia Marina in both World Wars before joining the Soviet Navy as the Novorossiysk. Her keel was laid down on 24 June 1910 at Cantieri Ansaldo, Genoa...

 originally mounted 13 guns as built in 1915 and 1914. These ships were rebuilt between 1933 and 1937 by removing the Q triple turret amidships and replacing guns in triple A turret, twin B and X turrets, and triple Y turret. Cavour carried Vickers

Vickers

Vickers was a famous name in British engineering that existed through many companies from 1828 until 1999.-Early history:Vickers was formed in Sheffield as a steel foundry by the miller Edward Vickers and his father-in-law George Naylor in 1828. Naylor was a partner in the foundry Naylor &...

 Mk G guns while Cesare carried Pattern T guns built by Elswick Ordnance Company. Odero Terni Orlando (OTO)

Oto Melara

Oto Melara is an Italian defence company with factories in Brescia and La Spezia. It was founded in 1905 as a joint venture of Vickers and Terni. During World War I, Vickers Terni produced many weapons with calibre 40 mm and upwards. In 1929 the company was renamed Odero Terni Orlando with the...

 re-bored the Vickers guns while the Elswick guns were re-bored by Gio. Ansaldo & C.

Gio. Ansaldo & C.

Ansaldo was one of Italy's oldest and most important engineering companies, existing for 140 years from 1853 to 1993.-From foundation to World War I:...

 Maximum gun elevation was increased to 27°.

M1936 guns

Andrea Doria class battleships

Andrea Doria class battleship

The Andrea Doria class was a class of dreadnought battleships of the Regia Marina . Only two were built, in the La Spezia and Castellammare shipyards, in Italy, between 1912 and 1915....

 Andrea Doria and Caio Duilio

Italian battleship Caio Duilio

Caio Duilio was an Italian that served in the Regia Marina during World War I and World War II. She was named after the Roman fleet commander Gaius Duilius. Caio Duilio was laid down on 24 February 1912 and after a year and two months of construction, she was launched on 24 April 1913...

 originally mounted 13 guns as built in 1916 and 1915. These ships were similarly rebuilt between 1937 and 1940 by removing Q turret and replacing guns in A, B, X, and Y turrets. Pattern T guns aboard Duilio were similarly rebuilt by Ansaldo while Mk G guns aboard Doria were rebuilt by OTO. Maximum gun elevation was increased to 30°.

Ammunition

The gun was loaded with four cloth bags each containing 44 kilograms (97 lb) of smokeless powder

Smokeless powder

Smokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...

. High explosive (HE) shells weighed only 458 kilograms (1,009.7 lb). Anticipated useful barrel life was 150 effective full charges (EFC).