I hate to be the bearer of bad news, but, the information presented in the Popovkas article in Conway's Warship 2015, indicates that the main armament of the Novogrod was two Krupp 11inch/20 caliber, 28 ton guns. Installed date: 1873, barrel length 5,588mm/20 cal, Bore/Rifled length 4,750mm/17cal,
As for the mounting "Each gun was indeed on an individual carriage, and these could be trained at different targets, although at some point their carriages would interfere with one another. They could also be lock so that they rotated together. The guns could be train the 180 degrees in 2-3 minutes, but despite the 'great rapidity of action' Reed observed, rate of fire was rather slow, one round per gun every ten minutes or so."The Vitse-admiral Popov mounted 12"/20 cal 41 ton Obbukhovskii guns mounted in the central barbette. "the mountings, of the Moncreiff 'disappearing type' were designed by Lieutenant L.A. Rasskazov, and were ordered from Armstrong in England. But by the autumn of 1876 Anglo-Russian relations were strained due to disturbances in the Balkans, and there were fears the war might break out before their delivery. It was therefore decided to build the mountings in Russia to a design based on the Novgorod's gun carriages, but scaled up to take the 12 in guns"I hope this helps.