You mean that the barrel would still be part of the turret, just connected to the \"hinge\" block? (Double selection? Is that allowed?)
If that was the case, you would only lose blocks to the hinge, not the blocks needed to prevent intersection, since the blocks are part of the same ship and making the physics engine check the barrel with the turret body would probably require more poking around in the engine than it\'s worth. Making sure the barrel doesn\'t intersect the ship is something that should be checked by the engine through.
Note on checking the barrel physics: we probably could just check the bounding box of the barrel to determine if it can rotate or not - And I also think this should be done with the turret body as well- it can\'t rotate through a wall.