what weapons does it carry?
Four 40-caliber 12-inch guns mounted in twin-gun turrets fore
Petropavlovsk-class battleship
The main armament of the "Petropavlovsk" class consisted of four 40-caliber 12-inch guns mounted in twin-gun turrets fore and aft of the superstructure. 
describe the petropavlovsk-class battleship An upper belt of armor was necessary and the weight required was gained by shortening the waterline armor belt, which left the ships' ends protected only by the sloping armor deck. Other changes included the replacement of the barbettes with turrets of the same type as used in the battleship and the substitution of QF guns for the original guns. This last change saved enough weight to permit four more six-inch guns to be added
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Petropavlovsk-class battleship [SEP] Armament
The main armament of the "Petropavlovsk" class consisted of four 40-caliber 12-inch guns mounted in twin-gun turrets fore and aft of the superstructure. They used hydraulic power for loading and traversing, but the ammunition hoists were electrically powered. Designed to fire one shell every 90 seconds, the rate of fire of the guns in service proved to be one round every three minutes. The structure of the turrets proved to be too weak to withstand extra-strength charges and had to be reinforced. The guns could elevate to a maximum of +15° and traverse 270°; each was provided with 58 rounds.