I could well be wrong here but perhaps its simply that part of the gun is closer to the camera than the 'near' CameraRange value. Try setting CameraRange 0.0001,1000 or something and see if that makes a difference.
EDIT - Actually, I think that's maybe what a couple of people were trying to say above.
EDIT - Actually, I think that's maybe what a couple of people were trying to say above.