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