Mark and Andy19K10, my first reaction to my own question was no, so your positive response surprised me.
I think they might have retained the 15" initially, in order to get the ship commissioned , after all it's easier to cast the projectiles for that rather than have to wait until new Brooke rifles, plus carriages designed to fit the turret were available.
As for the USN name, I can't offer an explanation.
What would the CSN have called her, again I don't know. If they had got into Mobile, then possibly CSS Mobile, At Charleston, Well CSS Charleston and, Chicora and Palmetto State already existed, Columbia was being built, Ashley and Cooper had bbeen assigned to the two new ironclads also under construction - doesn't leave a lot !