When the breech block is in the release position, the locking element is released by {HEAD ~ the control member} which moves in {TAIL ~ the breech block} parallel to the breech block 
moves in
When the breech block is in the release position , the locking element is released by { HEAD ~ the control member } which moves in { TAIL ~ the breech block } parallel to the breech block
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH