The term Battery originates from artillery, referring to a gun that fires before it has been pulled back.
In battery[edit | edit source]
The term In battery refers to a firing position where the bolt is fully forward locked.
Out of battery[edit | edit source]
The term Out of battery refers to the status of a weapon before the action has returned to the normal firing position. Depending on the design, it is also possible for a semi-automatic handgun to simply not fire upon pulling the trigger when in an out of battery state. In firearms where there is an automatic loading mechanism, a condition can occur in which a live round is at least partially in the firing chamber and capable of being fired, but is not properly secured by the usual mechanism of that particular weapon. The gas pressure produced at the moment of firing can rupture the not fully supported cartridge case and can result in flame and high-pressure gas being vented at the breech of the weapon, potentially creating flying shrapnel and possibly injuring the operator.