Glossary of Firearm Terms

This glossary of terms explains words, phrases, and concepts as they apply to firearms. You will hear almost all of these words in any class we teach. We provide them here for you to allow you to familiarize yourself with them before taking a class.

  • Action – a group of moving parts used to load, fire, and unload a pistol. (The “action” in a revolver contains the trigger, hammer, hammer-spur, cylinder, ejector, ejector rod, and other parts)
  • Barrel – The tube through with the bullet passes.
  • Bore – The hole inside the barrel of a firearm.
  • Bullet – The projectile expelled from a gun. It is not synonymous with cartridge. Bullets can be of many materials, shapes, weights and constructions such as solid lead, lead with a jacket of harder metal, round-nosed, flat-nosed, hollow-pointed, etc.
  • Caliber – The diameter of the bore, measured across from side to side, in decimal fractions of an inch. Example: a .45 barrel is 0.45 inches across. A .38 barrel is 0.38 inches across. A 9mm barrel is metric, so it is 9 millimeters across.
  • Cartridge – A single, complete round of ammunition.
  • Cleaning Kit – A kit containing various materials necessary for properly cleaning a firearm. They are often available for specific models, for handgun  rifle, or shotgun, or sometimes in kits that will clean all firearms regardless of caliber. Most often they contain cleaning rods of various lengths, bore brushes for various barrel sizes, cleaning patches, an oil cloth, jags for the cleaning patches, a double-ended nylon brush, and some form of cleaning and/or lubricating oil.
  • Double Action – A handgun mechanism where pulling the trigger retracts and releases the hammer or firing pin to initiate discharge.
  • Frame – The backbone to which all other parts are attached.
  • Handgun – any firearm that can be held and fired with one hand; either a revolver or a pistol.
  • Muzzle – The front end of a firearm, where the bullet exits, located at the end of the barrel.
  • Pistol – a handgun whose chamber is integral with the barrel that can be fired with one hand.
  • Primer – The ignition component of a cartridge, generally made up of a metallic fulminate or (currently) lead styphnate.
  • Revolver – a pistol that has a rotating cylinder containing a number of firing chambers. The action of the trigger or hammer will line up a chamber with the firing pin.
  • Rifling – The spirals (also called lands and grooves) inside the barrel of a firearm that cause the projectile to spin when it leaves the barrel. Rifling helps keep the bullet spinning towards its target in a proper trajectory.
  • Single Action -A handgun mechanism where pulling the trigger performs only a “single action” – dropping the hammer. The hammer must be cocked each time. (See double-action above for the distinction).
  • Semi-Automatic – A firearm designed to fire a single cartridge, eject the empty case and reload the chamber each time the trigger is pulled