Chamber (firearms)

The cavity at the back end of a breechloader's barrel or cylinder in which the cartridge is inserted before being fired

The chamber is that part of a firearm into which the cartridge is loaded.[1] The chamber is also the place the cartridge is fired from.[2] In a breech-loading weapon the chamber is directly behind and in line with the barrel.[1] In a revolver there are multiple chambers contained in a revolving cylinder.[1]

Diagram of a firearm chamber. Figure A is unloaded or empty. Figure B is loaded with a cartridge

The typical number is 6, which is the reason for the nickname Six Shooter and indicates the cylinder has six chambers each holding one cartridge.[3] Most rifles and pistols have a single chamber.[4] To chamber a round means to load a cartridge into the chamber.[5]

Semi-automatic weaponsEdit

AR-15 semiautomatic rifle

In a semi-automatic firearm, the weapon can fire a bullet each time the trigger is pulled (until the magazine is empty).[a][5] A semi-automatic firearm can be a pistol, rifle, or shotgun. Each time the trigger is pulled, the gun fires, the spent shell is ejected and a new round is loaded into the chamber.[7] The semi-automatic is a very popular choice for sporting use.[7]

Semi-automatic pistols and rifles use the pressure of the fired cartridge to move the slide backwards.[8] A fraction of a second later, the slide moves forward loading a fresh cartridge into the chamber.[8] The magazine uses a spring to feed one cartridge at a time into the chamber.[8]

Fully automatic weaponsEdit

Fully-automatic firearms are those that automatically reload and fire again repeatedly as long as their triggers are depressed and they still have ammunition in their magazines. Fully automatic weapons are not for sporting use but are used by police and militaries. An assault rifle is "a gun that can shoot many bullets quickly and that is designed for use by the military".[b][10] Like semiautomatic firearms, automatics have a single chamber.

Manual loading weaponsEdit

A manually loaded firearm is one in which the chamber is loaded by hand each time the weapon is fired. For example, a Bolt action rifle ejects the spent cartridge when the bolt is pulled back, then loads another cartridge into the chamber when the bolt pushed forward (and locked).[5]

A lever action rifle does the same thing when the lever is moved down (ejects the spent cartridge), then up (loads a new round in the chamber).[5] There are also single shot pistols, rifles and shotguns in which the breech is opened to eject a spent shell, then the shooter loads a round into the chamber manually.

A popular type of manually loaded firearms for sporting and hunting use is the pump action shotgun. Here, a sliding handle (usually located under the barrel) is moved backwards to eject the spent shotgun shell, then when moved forward it loads a fresh shotgun shell from a tubular magazine.


  1. This is why, for safety reasons, a shooter's finger is never placed on the trigger until the shooter is ready to fire the weapon.[6]
  2. Fully automatic firearms and semiautomatic firearms often look very similar.[9] This is why many mistake a semiautomatic rifle for a fully automatic (or assault rifle) rifle designed for military use.[9]


  1. 1.0 1.1 1.2 Russ Chastain (10 May 2016). "Definition of Gun or Firearms Chamber". About Sports. Retrieved 19 August 2016.
  2. "Firearms Definitions" (PDF). Tennessee State Courts. Tennessee Courts System. Retrieved 19 August 2016.
  3. "six-shooter". Memidex. Retrieved 19 August 2016.[permanent dead link]
  4. "What Is a Gun? A Primer". New York City LENS. Retrieved 19 August 2016.
  5. 5.0 5.1 5.2 5.3 Brian R. Johnson, Crucial Elements of Police Firearms Training (Flushing, NY: Looseleaf Law Publications, 2008), pp. 62–63
  6. Robert Farago (12 January 2011). "Keep Your Finger Off The Trigger Until You Shoot". The Truth About Guns. Retrieved 19 August 2016.
  7. 7.0 7.1 Adam Weinstein (21 December 2012). "A Non-Gun-Owner's Guide to Guns". Mother Jones. Retrieved 19 August 2016.
  8. 8.0 8.1 8.2 "Semi-Automatic Pistol Components and Operations". Level 1 Firearms Safety and Training. Archived from the original on 10 August 2016. Retrieved 19 August 2016.
  9. 9.0 9.1 Debbie Lord (14 June 2016). "Assault weapon vs. assault rifle: What is the difference?". Journal-News/Cox Media Group. Archived from the original on 20 August 2016. Retrieved 19 August 2016.
  10. "assault rifle". Merriam-Webster Dictionary. Retrieved 19 August 2016.