Now that's a bit of a moot point. The RN referred to all mountings, unarmoured, turret or barbette style, as mountings, but, technically, the last ship in the Andreew with turrets was the Hood (the one at Portland, that is). All later BS & BCs had barbettes, the armour being fixed to the ship, whereas in a turret the armour is part of the rotating mass, but the terms seem to have been used pretty much indiscriminately.