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