What Is the "Chamber" on a Gun or Firearm?

Flobert rifle chamber
The chamber in this photo is the hole in the center of the breech, over to the left of the arrow. Photo © Russ Chastain

The word "chamber can be used either as a noun or verb when it is used in language related to firearms shooting.

"Chamber" Used as a Noun

When used as a noun, the word"chamber" refers to the portion of a breech-loading gun or firearm in which the ammunition cartridge is contained when the cartridge is in a position for shooting the gun. 

In rifles and pistols, the chamber is typically located at the rear end of the gun's barrel.

A revolver has multiple chambers, arranged in a circular pattern in the gun's cylinder.

Another noun form is the word"chambering," which refers to the size of the cartridge that fits a particular gun. For example, if a gun is intended for use with the 30-06 cartridge, its chambering is said to be 30-06.

"Chamber" Used as a Verb

When used as a verb, "chamber" usually means "to place a round of ammunition into the chamber." This may be done by inserting a cartridge into the chamber directly from your hand, or by working the gun's mechanical action to do so. In a  semi-automatic pistol or rifle, the action of the gun automatically chambers a new round as the previous round is fired. On a bolt-action, lever-action, or pump-action gun, the new round is chambered by physical action from the shooter. 

In another, less common usage, "chamber: may be used as a verb to refer to the act of cutting a chamber into a firearm.

To chamber, a new barrel means to use a special reamer to cut a cavity, or chamber, of specific dimensions into its rear end. The dimensions of the barrel's chamber and bore dictate what type of ammunition may be safely used in it.