here is a possible idea for you - this is the system I used for the guns on HMS Exeter which is of a scale of 1:96 - I used a miniature servo for elevation; also a servo which is able to drive 180 degrees for the main rotation of the gun.
The servo is mounted underneath and where you locate the arm on the servo, I made a tube which goes all the way through the barbet into the base of the gun, this is the connection which rotates the gun.
The cable from the miniature servo which elevates the barrels run inside the tube and comes out through a small hole at the base of it.
I also use an electronic servo slower and stretcher from Forge Electronics to slow the movement of the guns down to a scale speed. The only problem I had, was, I found when elevating the barrels up and down - they tended to be slightly jerky in movement and it took me a while to work out how to dampen this - and all things equal - the simplest solution came to rest - make a rubber wedge
which fits between the side of the barrel mounting and the side of the casing, causing a little bit of resistance.
Hope this is of some help.