The issue of turrets in southern ironclads is kind of interesting. Southern constructors and naval officers were clearly aware of the potential advantages of a turret. But I believe there was a philosophical clash among the Naval officers about the relative value of the turret vs the casement layout. Turrets had been proposed from the beginning of the century, but presented some limitations for the designer. They also created concentrated loads which had structural implications. Oddly, the low rate of fire of muzzle-loading cannon may have worked in the turrets favor, giving the gun crew more time to get powder and shot into the turret for reloads. There was a strict limit on how much "ready" ammunition could be carried in the turrets and in some turret designs, the turret had to be in a specific alignment to allow access while under fire. Constructor Porter is sometimes criticized for his casement designs, but in practice they did what they were designed to do. The layout was more familiar to Naval officers as they approximated an enclosed gundeck similar to those found in the larger classes of existing unarmored vessels (frigates and ships of the line). They were floating batteries, carrying the heaviest naval rifled guns (and occasional broadside smooth-bores) that the Naval gun factories could produce. After 1862, I don't believe that any of the domestically produced ironclads were ever claimed to be sea-going. They didn't have to, to achieve what Mahan later called a doctrine of "a fleet in being". They just had to survive and be there when needed. At the risk of taking up too much space, I'd like to point out that in practice both Confederate and Union ironclads are an early example of what we call today a "weapons system". Virtually none of them were effective weapons without substantial support services. They had short endurance, poor living aboard qualities, none of them except the fragile Galena and Keokuk were good sea boats, and they often required tows between stations. The confederates knew how to build a Coles type man-actuated turret and decided to pass on them until the Columbus proposal. At least two specialized vessels with twin casements at the ends of the vessel to house single pivoted rifled cannon (probably Brookes) were building at the end of the war. If I remember correctly, one was to have engines and propellers on both ends. I think that one of the essential arguments that found its way into Porter's designs, was the thoughtful criticism that CDR Cooke of the Albemarle made about the pivot guns. He felt that the time required to move them from port to port was a tactical problem. His clash with a squadron of Union gunboats and the need to engage on both sides simultaneously had pointed out the drawbacks of single pivots guns at the ends of a casement. Cooke's suggested improvement in future vessels of the class was to add a pair of broadside guns. There is reason to believe that this was incorporated into the design of the Fredricksburg. In the smaller, shallow draft ironclads, the depth of framing of the hulls was limited. A casement system allowed the concentrated weights of powerplant, coal, guns and armor to be distributed along the length of the vessel, minimized hogging and sagging. In the Casco class monitors (shallow draft), it became necessary to remove the turrets to give the hull sufficient buoyancy so they wouldn't be swamped in choppy water. At Richmond, they tried a type of compromise protection, adding gun-shields on the Nanesmond. There is a sketch of this vessel (basically one of the few completed Maury gunboats) with such a structure forward at the forward pivot position. I don't know how heavily it was armored. Possibly just with boiler iron tin-clad style.