{HEAD ~ The locking mechanism} has {TAIL ~ a breech block} which is locked with the stock and which can be released by a spring biased control member 
has
{ HEAD ~ The locking mechanism } has { TAIL ~ a breech block } which is locked with the stock and which can be released by a spring biased control member
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH