Tank Turret Problem

Hi there,
i build a tank with a hull (Basic Piece) and a turret Layer.
i want the turret to be rotateable. so i put some “can rotate” in the definition, like this.

Basic Piece (hull)
can rotate (SHIFT+Left/Right) (rotates hull inverse)
Layer (turret)
can rotate (SHIFT+Left/Right) (rotates everything)
can rotate (CTRL+Left/Right) (rotates everything)

works, but looks ugly…

[attachment=0]behold the mighty paint skills.jpg[/attachment]

Any ideas to realise tank turrets or how to get rid of the fuzzyness?