320 mm / 44 Mod. 1934

By the decisions of the Washington Maritime Conference of 1922, the construction of new battleships was prohibited until 1931 . However, a number of exceptions were made to the signed agreement. In particular, Italy and France , which at the time of the signing of the treaty had the weakest militant battleships, received the right to build, starting in 1927, two battleships with a total displacement of not more than 70,000 tons ^[2] . The London Naval Treaty of 1930 , which extended the moratorium on the construction of battleships until 1936 , retained this right for Italy and France. However, initially both parties were in no hurry to take this opportunity. In the early 1920s , both countries were in a difficult financial situation ^[3] , later on, the French military and political leadership preferred to spend money on land defense, primarily on the Maginot Line , and the opinion about dying battleships. During the First World War, the Italian battleships did not prove to be particularly useful ships ^{[4] [approx. 1]} . and as a result, a theory emerged in the Italian navy about the predominant role of aviation and submarines in a future naval war. In addition, the leadership of both countries did not want to provoke a "battleship" arms race and preferred to take a wait and see attitude.

In 1928, the government of the Weimar Republic announced the laying of the “battleship” “Deutschland” - the lead ship in the series of “pocket battleships” of the German fleet ^[5] . This news aroused great concern of the leadership of the French fleet, and despite opposition from the French parliament, in 1931 it secured the allocation of funds for the construction of a battle cruiser ^{[approx. 2]} "Dunkirk" ^[6] . This ship was laid in 1932 . It had a standard displacement of 26,500 tons , a speed of about 30 knots, and was armed with 330 mm guns with a long firing range ^[7] . Although the French positioned him as a hunter for the German "pocket battleships", in the Italian naval circles, the construction of the "Dunkirk" was seen as a step towards changing the status quo in the Mediterranean . By the beginning of the 1930s, the Italian fleet had only two battleships of the Andrea Doria type, armed with 305-mm guns and developing speeds of less than 22 knots. It was believed that a French ship could destroy both Italian battleships, using its advantage in the speed and range of main guns ^{[8] [approx. 3]} .

The command of Regia Marina urgently began to develop a response. The most obvious was the construction of new battleships. The design of future battleships of the Littorio type was actually begun in 1932 ^[9] . But this meant that the first new battleship would come into operation no earlier than six to seven years ^[8] . This time period meant that in the future there would be a period when the Italian fleet would have nothing to oppose the French battlecruiser. As a result, in 1932 a decision was made to radically modernize two battleships of the Conte di Cavour type and already in 1933 work began on both ships. The project involved the replacement of 60% of the original designs. The hull was lengthened, the power plant was completely replaced, armor was strengthened, armament was changed ^[10] . But the question of the replacement of the main caliber guns was especially acute, without which the modernization of battleships lost their meaning ^[10] .

It was impossible to establish new artillery of the main caliber on the battleships. Firstly, the creation of new guns and their installations required time comparable to the construction of a new battleship. Secondly, this would lead to an unacceptable reduction in the number of guns. In addition, the fleet was already working on the creation of new 381-mm guns for battleships of the Littorio type and was not able to implement another similar project ^[10] . As a result, it was decided to drill guns of the main caliber of battleships such as "Conte di Cavour", as far as possible according to the ultimate strength , to develop new shells , and also to increase the elevation angle of the guns ^[11] .

Battleships of the Conte di Cavour type in the initial version carried 13,305-mm guns in five towers - three three-guns and two two-guns. During the reconstruction, the middle three-gun tower was removed, and the guns of the remaining ones were subjected to serious alteration. Thanks to the wire construction of the guns, it was possible to increase their caliber without changing the external dimensions ^{[approx. 4]} . The inner tube was removed, and then part of the wire winding was removed. A new pipe, caliber 320 mm, was inserted into the expanded channel. Cutting was constant, right-sided, with a step of 30 calibers. The relative length of the gun was reduced and now amounted to 43.75 calibers, but officially the guns were called 320 mm / 44 . The rest of the design of the guns remained unchanged. The guns retained the piston lock of the Velin system with a pneumatic actuator. Since the guns of the battleships initially had some difference in design, the conversion of the Armstrong guns that were on the Cayo Duilio and Giulia Cesare was entrusted to the Ansaldo company, and the work on the Vickers guns that were available on the Conte di Cavour and Andrea Doria ”produced the company OTO . Accordingly, the former received the designation Mod. 1934 , and the second Mod. 1936 . The characteristics of both models were the same ^[12] .

As a result of the work done, the muzzle energy of the gun increased by 13.4%. The mass of armor-piercing shell increased by 16%. However, at the same time, the reduced strength of the barrel forced to limit the maximum pressure of the powder gases in the barrel to 3100 atmospheres , which led to a certain drop in the initial velocity of the heavy projectile. The survivability of the barrel was also low - 150 rounds. However, the low survivability of the trunks was a characteristic feature of almost all samples of Italian naval artillery. ^[13]

Two types of shells were used - armor-piercing and high-explosive . Their length was the same, but because of the larger size of the chamber , the HE shell weighed less - 458 kg compared to 525 kg in armor-piercing. The explosive content in the armor-piercing projectile was about 2% ^[14] , which fit into the mainstream of the tendency to reduce the weight of explosives in armor-piercing shells that appeared in the 1930s and 1940s ^[15] . The propellant charge still consisted of four caps and had a total weight of 175 kg ^[16] .

Since 1936, the Italian fleet switched to the use of two new grades of gunpowder as a propellant. NAC gunpowder was produced by Dynamite Nobel and consisted of 27% nitroglycerin , 66% nitroacetyl cellulose and 7% centralite . FC4 , manufactured by Bombrini-Parody-Delfino, included 28% nitroglycerin, 64% nitrocellulose , 4% phthalate , 4% centralite and 1% petroleum jelly . In terms of effectiveness, these compounds were inferior to British and German gunpowders. The Italians did not have flameless gunpowder for large-caliber artillery, which made night shooting difficult. In addition, the Italian standards for the manufacture of ammunition allowed for too significant deviations, which led to a large spread of shells in the salvo. This problem also affected the 320 mm / 44 Mod. 1934/1936 ^[12] .

320 mm / 44 Model 1934

• Patyanin S.V. Damned battleships. "Caesar", which became the "Novorossiysk". - M: Collection, Yauza, EKSMO, 2011 .-- ISBN 978-5-699-46587-3 .
• Campbell J. Naval weapons of World War Two. - Annapolis, Maryland: Naval Institute Press, 1985 .-- ISBN 0-87021-459-4 .