Abstract: A firearm is provided which includes a stock having a barrel end face, a generally longitudinally-extending primary bore formed therein and opening onto the barrel end face, and at least one generally transversely-extending, internally-threaded ancillary bore formed therein one end of which opens onto the primary bore and the other end of which opens onto a lateral face of the stock. The firearm also includes a double barrel having a barrel end plate and a bolt secured to the barrel end plate having an annular groove which bolt is demountably and rotatably received within the primary bore with the groove thereof being positioned such that it opposes the ancillary bore. At least one set screw is threadably receivable in the ancillary bore and has an inner end which is configured and dimensioned to permit mating engagement thereof with the annular groove, so as to retain the bolt in the primary bore while permitting rotation thereof and, in turn, the double barrel.