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