Gas powered air guns comprise a very large portion of the guns used in recreational sports. From BB and pellet guns to paintball guns, gas powered air guns all use a system that uses compressed gas to fire a projectile.
Most of these guns use a compressed common gas such as carbon dioxide or simple atmospheric air. Gas powered guns allow this compressed gas into the chamber to force the awaiting projectile out the barrel. Many guns also use the blowback from the chamber to reset the firing action. Some of these guns use commercially available carbon dioxide (co2) cartridges, which are used until spent and then discarded. Others use air tanks of various sizes that are filled with a hand pump.
The chamber contains the ammo until it enters the barrel. The action of the gun controls the flow of gas to the chamber, based on the users trigger action. The bolt is attached to the action and is the mechanism that loads the ammo and seals the chamber for firing.
The action is the mechanism that converts the trigger squeeze into a shot. The action generally comprises several springs that apply tension to the bolt and hammer. The hammer opens the control valve of the gas chamber briefly. When the trigger is pulled, the action is released and a series of springs force the hammer to spring back and hit the pressure valve of the gas chamber, which allows a burst of gas into the chamber through the valve tube, forcing the ammo out of the barrel. The valve tube enters the chamber through a hole that is bored in the centre of the bolt.
In most gas powered air guns, there are several valves that control the short bursts of air that create propulsion. The most important valve is the pressure valve that is struck by the hammer. The pressure valve is held shut by a very strong tension spring and maintains a seal until the hammer strikes.
Blowback is the reaction from the valve opening and releasing pressurised gas into the chamber. Blowback is used to reset the bolt and action to the initial position.