Lastly, you have your gas airsoft gun. Gas guns come in three types: CO2 (sometimes referred to as “red gas”, propane or “green gas” (propane mixed with silicone lubricant), and HPA (high pressure air). HPA guns are effective but more rare and controversial, so we won’t be covering them just yet.
Propane or “green gas” guns are the most commonly used gas type. They come in the green 16 ounce mini-propane tanks that you use when camping.
CO2 gas usually comes in a 12-gram cartridge (think of the paintball guns or BB guns you used as a kid). They are the lower tier of gas airsoft guns. CO2 is more powerful, but less consistent.
Gas guns are the most realistic-feeling (and looking) airsoft guns available. They use gas blowback, which gives your gun recoil, and their instant trigger response feels like you are holding a real gun in your hands. They tend to have a larger magazine capacity, and also make great sidearms or backup guns. Gas guns have less shots per gas cylinder than an AEG does per battery, but gas cylinders can be switched out in the middle of a match or sim.
Gas guns have their cons. If you play outdoor in an area where the winters or cold, or are going to a match/mil-sim/tournament in cold weather, gas guns will fail; the gas loses its pressure in the cold, and be weak, unpredictable and inaccurate with your shots. Gas rifles also hold much fewer magazines, and so are limited in the number of shots that can be fired, as airsoft guns go through gas quicker than they go through batteries. CO2 cartridges often last only for the duration of the clip.
As the gas pressurizes the inside of the gun, gas guns also tend to wear down the fastest, yet are the most expensive rifles on the market. Gas guns have a “cooldown” when firing too rapidly. Shots can be inconsistent (remember paintball guns, especially running on CO2?) and less accurate. In addition, the recoil is the highest of the guns on the market, as the gas blowback will make your gun kick. While a lot of players like the recoil because of the added realism, an automatic gas gun will recoil just like in real life.