When {TAIL ~ the breech block} is in {HEAD ~ the locked position}, a clearance is provided between the locking surface and the locking element on the side facing away from the barrel 
When { TAIL ~ the breech block } is in { HEAD ~ the locked position } , a clearance is provided between the locking surface and the locking element on the side facing away from the barrel
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH