Abstract: An enclosure holds an air mover, a switch, and a power source such as one or more electric storage batteries. A hollow outflow tube receives air drawn into the enclosure by the air mover. An end of the outflow tube has an outer diameter selected to pass through the action of a firearm and into the firing chamber. When the end of the outflow tube is inserted into the chamber and the air mover is turned on, ambient air is drawn into the enclosure, through the air mover, through the outflow tube, into the chamber, through the bore of the barrel, and out the muzzle, thereby cooling the firearm's barrel. When the end of the outflow tube is inserted into a chamber, an embodiment provides a visual indication that the chamber does not contain a cartridge.