203 mm /53 Italian naval gun

The 203 mm/53 Ansaldo was the main battery gun of Italy's most modern Washington Naval Treaty heavy cruisers. This treaty allowed ships of not more than 10,000 tons standard displacement, and with guns no larger than 8 inches (203 mm), to be excluded from total tonnage limitations on a nation's capital ships.

Description
These built-up guns consisted of a liner, A tube, and full-length jacket with a hydraulically operated Welin breech block. Each heavy cruiser carried 8 guns mounted in 4 twin turrets with maximum elevation of 45°. The 181 tonne turrets mounted both guns in a common cradle with centerlines only one meter apart. This mounting practice conserved weight, but mutual interference increased dispersion during salvo fire. Each gun could fire approximately four rounds per minute. The M1929 guns aboard Bolzano were slightly lighter than the M1927 guns aboard earlier cruisers.

Ammunition
The smokeless powder charge was contained in two cloth bags. Infobox velocity and range is for the armor-piercing (AP) shell with a 51 kg (112 pound) powder charge. High explosive (HE) shells weighing 111 kg used a 42 kg (92 lb) powder charge for a velocity of 940 m/s (3100 ft/sec). The AP powder charge was reduced to improve performance. AP shell velocity was 900 m/s (2950 ft/sec) for a maximum range of 31 km with the HE powder charge.

Naval service
Fiume, Gorizia, Pola, and Zara mounted M1927 guns.

Bolzano mounted M1929 guns.

Trento and Trieste mounted earlier 203 mm/50 Ansaldo M1924 guns. These guns initially used the same AP projectile with a 47 kg (104 lb) powder charge to duplicate the ballistics of the HE powder charge in later 203 mm/53 guns, but the powder charge was similarly reduced with experience.

Weapons of comparable role, performance and era

 * BL 8 inch Mk VIII naval gun British equivalent
 * 203mm/50 Modèle 1924 gun French equivalent
 * 20.3 cm SK C/34 Naval gun German equivalent
 * 20 cm/50 3rd Year Type naval gun Japanese equivalent
 * 8"/55 caliber gun US equivalent