 Koldun was designed to be armed with a pair of 9 @-@ inch ( 229 mm ) smoothbore muzzle @-@ loading guns purchased from Krupp of Germany and rifled in Russia , but the rifling project was seriously delayed and the ship was completed with nine @-@ inch smoothbores . These lacked the penetration power necessary to deal with ironclads and they were replaced by license @-@ built 15 @-@ inch ( 380 mm ) smoothbore muzzle @-@ loading Rodman guns in 1867 – 68 . The Rodman guns were replaced around 1876 with the originally intended nine @-@ inch rifled guns . 
