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