The 305 mm /46 Model 1909 was a naval gun that was the main armament of two classes of Italian dreadnought battleships and one unique dreadnought of the Regia Marina built at the beginning of World War I. Many of these guns were later modified to 320 mm Model 1934 and 320 mm Model 1936 naval guns by boring out their barrels, adding new liners and developing new ammunition. Wikipedia