How does a CO2 airgun work?

The gun pierces a CO2 cartridge or draws from a bulk tank, exposing the pellet path to liquid CO2 that is constantly evaporating into a high-pressure gas.

At room temperature, that gas sits at roughly 850 to 1,000 PSI. When you pull the trigger, a valve opens briefly to release a metered puff of gas behind the pellet. The cartridge stays usable until the liquid CO2 is exhausted and gas pressure drops too low to cycle the gun.