When they they are closed up, the entire length of the barrel lug is sandwiched between the receiver walls. When the gun is open, only a small part of the lug is inside the receiver. I would guess that the further the guns are open, they looser they are. In addition, when the guns are closed, the rib extension would tend to prevent any side to side play and the rotary bolt is also exerting pressure on it. In short, there is a lot more surface area preventing side to side motion when the gun is closed than when it is open.
Last edited by B Frech; 06/13/07 08:59 PM.
