an unmodified selected caliber handgun having {HEAD ~ a barrel} receiving cavity with {TAIL ~ a mounting surface} for receiving a live ammunition firing barrel 
an unmodified selected caliber handgun having { HEAD ~ a barrel } receiving cavity with { TAIL ~ a mounting surface } for receiving a live ammunition firing barrel
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH