Cannone-Mitragliera da 37/54 (Breda)
The Cannone-Mitragliera da 37/54 (Breda) was a automatic anti-aircraft gun produced by the Breda company in Italy. It was used by both the Regia Marina and the Regio Esercito during World War II, with the former using it as the standard light anti-aircraft weapon on its battleships and cruisers. Nazi Germany used captured weapons after the surrender of Italy in 1943 as the "3.7 cm Breda (i)". Design. The Model 1932 was water-cooled while Models 1938 and 1939 were air-cooled. The gun was fed by a flat magazine holding six  rounds which could be loaded one after another to maintain a high rate of fire. It was possible to select alternate rates of fire, either 60, 90 or 120 rpm. The twin mountings for Models 1932 and 1938 were very heavy and required a strong supporting structure. The single Model 1939 (fitted on the "Andrea Doria"-class and "Littorio"-class battleships), was instead a single collapsible mount, which also had much less vibrations than its predecessors thanks to the addition of an equilibrator. This meant it could also fitted on smaller warships. Ship classes that carried the Breda 37/54 include: The Breda  37/54 was also fitted in the CANSA FC.20bis ground attack aircraft prototype in its variant "Model 39 37/45". Performance. Although appreciated in the Regia Marina, overall this gun was of limited efficacy because of its gas-operated action (which reduced its rate of fire) and its substantial vibrations (due to their non-recoiling mounting) which impaired accuracy. Instead the single collapsible model, which largely eliminated the latter issue, was seen as a definite improvement, while still being rather heavy and with its production being insufficient to satisfy the needs.