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According to Wiki - a firearm is a portable gun, being a barreled weapon that launches one or more projectiles often driven by the action of an explosive force.

That sounds about right, so let's call them just "guns". When you say a gun, then usually follows a specification:

• calibre - e.g. 9mm or .357, it is practically the barrel inside diameter in milimeters or inches
• action type - automatic, semi-automatic, revolver, pump, lever
• barrel length - short for handguns and long for rifles or shotguns
• manufacturer - Glock, Ruger, Beretta