With this remix of @ZeBobs original model I created a base for the turret to be able to spin. Check the post printing steps for instructions. Also did some cuts on the body so I could print without supports. The source file is attached so you can modify the tolerances and the model itself, enjoy.
Glue the Outer Left to the Main Left. Then put some glue in the connection cylinders and insert them until they reach the Outer Left.
Glue the Turret Base to the Turret. At this point verify if the turret base can spin freely within the two main parts of the Hull. If necessary sand it a bit.
Glue the right side to the left with the Turret Base in between the two parts of the hull.
Try to sand a bit with P500 and P600 sanding paper and water.
Glue the remaining elements.
Used Fusion 360 to cut the model and create a rotary base for the turret. The source file is attached.