Chamber (firearms)
In firearms, the chamber is the cavity at the back end of a breechloader's barrel or cylinder in which the cartridge is inserted before being fired. Rifles and pistols generally have a single chamber integral to their barrels, but revolvers have multiple chambers in their cylinder, and no chamber in their barrel. Thus rifles and pistols can usually still be fired with the magazine removed as long as a cartridge is inserted into the chamber, while a revolver cannot be fired at all with its cylinder swung out.
The act of chambering a cartridge means the insertion of a round into the chamber, either manually or through the action of the weapon, e.g., pump-action, lever-action, bolt action, or automatic action generally in anticipation of firing the weapon, without need to "load" the weapon upon decision to use it.
In firearms design or modification, "chambering" is fitting a weapon's chamber for a particular caliber or round, so a Colt Model 1911 is chambered for.45 ACP or.38 Super, or re-chambered for.38/.45 Clerke.
