Sorry this is so late.
As for Naval guns yes we can pretty much safely put them in the top tier as the best around in the 1860's. But there were a whole line of Dahlgren guns, the IX inch was plenty capable as the lighter guns on many ships and fine for the needs of the Union Navy, but outclassed if it had been used against a real navy, the larger also very common XI inch was the best of the bunch for power, reliability, and ease of use.
The XI inch gun in particular was essentially the same in performance to the vaunted British 68 pounder which made up most of the original main battery on HMS Warrior.
The problem is that it should be kept in mind that even then effective rifled guns were much more effective and capable of penetrating armor more efficiently and were better weapons for fighting other ironclads.
Some previous threads speaking to the performance of the Dahlgren, British smoothbores, and comparisons to both rifled guns and British and French ironclads. Essentially the Union navy was lucky it never had to face a first rate ocean going ironclad with the cannons it had on hand, but was perfectly serviceable as a riverine and blockade force.
https://www.reddit.com/r/AskHistorians/comments/2ffh5o/how_effective_were_ironclad_warships/?