A CO2 air rifle shoots BBs or pellets (and some can do both) using a CO2 cylinder as a power source. There are also automatic air rifles.For a reasonable price, they provides hours of shooting fun without the need for an external high-pressure air source or the hassle of pumping or tightening. So start looking for the perfect Co2 air soft guns now.Co2 air soft guns usually use one or two 12 gram cartridges (or sometimes the larger 88 gram cartridge) and are very consistent at higher temperatures as long as the cartridges contain liquid CO2 (aka Co2, CO-2 and Co-2).