After many iterations I think I have the ball turret shape sorted out.
Here are the patterns I printed out and stuck to some cereal packaging:
These were cut out to form a main center tube and two end caps.
This is the (temporarily) assembled ball turret. The two end caps can rotate around the center axis, and the space marine gunner sits on top of it. The cutout piece will form a removable hatch.
Here is the ballturret in the socket, with the space marine gunner inside. It will now get the gun barrels glued onto the side disks, so that the entire ballturret can yaw left and right, while the guns can pitch up and down.
The gunner will get a control panel in front of him too.
The piece is still very rough, with cardboard fibers sticking out everywhere. It'll be cleaned up nicely, I promise
