Gas operated firearms use the energy from expanding gases produced when a cartridge is fired to cycle the action of the firearm. This mechanism allows for automatic or semi-automatic firing, as the gas is redirected from the barrel to operate the bolt or slide, ejecting the spent cartridge and chambering a new round. These firearms are commonly found in military and law enforcement applications, as well as in civilian use. Examples include the AR-15 and AK-47, which utilize gas operation to enhance firing speed and reliability, making them popular choices for various shooting activities.