Most firearms do not have literal batteries. But a firearm is said to be in battery when the breech is fully closed and locked,
ready to fire. When the breech is open or unlocked, the gun is out of battery and no attempt should be made to fire it.
A semi-automatic is out of battery when the slide fails to come all the way forward again after the gun has fired, making it
dangerous or impossible to fire the next round. This condition can be created by a misfeed, a dirty gun, weak springs,
the shooter's thumbs brushing against the slide, riding the slide, or any of several other causes.