Abstract: A metallic cartridge plug corresponding in dimensions to cartridges used in a firearm and having a screw disposed through an opening in its closed end is insertable within the firing chamber of the firearm and is free to rotate therein about its longitudinal axis. The threaded end of a telescoping rod is inserted through the barrel of the firearm and threaded into the screw disposed on the cartridge plug. A cap having a diameter substantially in excess of the bore diameter of the firearm is affixed to the outer end of the telescoping rod, such that the telescoping rod can be telescoped to bring the cap flush against the muzzle end of the barrel. The telescoping rod can not be unthreaded from the cartridge plug without simultaneously pulling and turning the cap affixed to the telescoping rod.