the cutter rod 31 also has a hex head 37 or some other device for gripping the rod at its proximal end the expander rod 32 has tapered male threads 38 at its distal end and a hex head 36 or some other device for gripping the rod at its proximal end both the cutter rod 31 and the expander rod 32 have a lock ring 39 which is positionable on the shanks of the rods once a position on the shank is selected the lock ring 39 may be locked in place on the shank of the rod the lock rings 39 comprises any locking mechanism which is known to persons of skill in the art the bore cutting tool 30 is used to cut a bore expansion chamber 20 in a rifled bore by inserting the cutter rod 31 into one end of the bore and inserting the expander rod 32 into the opposite end of the bore for illustration assume that the cutter rod 31 is inserted into the muzzle end and the expander rod 32 is inserted into the breach end a measurement is taken to determine how far into the bore the bore expansion chamber is to be cut from the muzzle end the lock ring 38 on the cutter rod 31 is locked in place on the shank of the cutter rod 31 so that the cutting edges 36 extend to the side of the intended bore expansion chamber 20 opposite from the muzzle 9 the cutter rod 31 is then inserted into the muzzle end of the bore until the lock ring 39 contacts the muzzle the expander rod 32 is then inserted into the breach end of the bore until the.