Priced somewhere between spring and electric powered guns, gas powered Airsoft guns can be used for single shot, semi-automatic or fully automatic operation. They tend to be used by collectors due to their very authentic look and feel in use, but serious gamers will tend to use electric Airsoft guns for regular use. The most common gas used is a mixture of polysiloxane lubricant and propane known as 'green gas'. Less commonly used are 'red gas', a chlorofluorocarbon that has been banned for use in the USA and many other countries due to its ozone-depleting properties, and compressed CO2, nitrogen or air. Compressed gases need high operating pressures that can tend to cause damage to the guns due to the pressures involved, particularly damage to the bolt and slide.
Gas Powered Airsoft Guns: Pros A major advantage of gas guns over spring guns has already been stated: they can be used for semi- and fully automatic operation, whereas spring guns are limited to single shot use. This is because the spring has to be tensioned back after each individual shot. An electric mechanism cannot be used in many pistols due to the size constraints imposed by their design. It is just not possible to manufacture an electric Airsoft pistol that replicates the genuine guns produced by many manufacturers. Those that collect true replicas will therefore tend to choose a gas-operated pistol rather than sacrifice authenticity.
Another benefit of a gas Airsoft gun is the 'blowback' mechanism. This mechanism is not available on all gas guns, and costs a bit extra, but if you want the authentic feel of a gun when firing then it's worth the extra cost. With an Airsoft gas blowback gun, the slide moves back with each shot and gives you a recoil effect - just like in a real gun. Many people choose gas as their preferred Airsoft automatic rifle because of this degree of realism - but make sure that the clip can hold a good number of bbs or you won't be shooting on auto for very long! You can get blowback with other forms of Airsoft power, but gas is best and most gas guns are now fitted with it.
Gas Powered Airsoft Guns: Cons The regulation and distribution of gas in an Airsoft gun means that gas guns are more complex mechanically than spring guns and electric guns, although are priced somewhere between the two. Some believe the simplicity of the spring guns in play make them more convenient, and when also taking cost into consideration, tend to prefer spring powered Airsoft guns to gas. Others prefer to go for electric or nonblowback gas guns for certain specialist uses such as target shooting.
There is a potential problem associated with liquefied gases such as green gas, in that the gas is very cold when in liquefied form. It can therefore cool down the mechanism of the gun in areas that are in contact with the liquid rather than its gaseous form, and this can slow down its firing rate and range. This is particularly so in automatic mode. Not only that, but if the propellant is moved at high velocities through narrow apertures, it can freeze up and not only slow the gun down but also stop it altogether. Many believe this to be unlikely, but it can happen. You could use CO2, compressed nitrogen or air, but that can also damage the mechanism.
Blowback or Non-Blowback? Many buy gas guns for their realism, but electric or spring powered Airsoft guns for play. A problem associated with using blowback with automatic firing in gaming is that it uses gas up quickly, and you may have to carry spare canisters around, slowing you up in the field. So many prefer not to use blowback or to use electric guns for play in auto mode. Not many gas guns are now available without blowback, but most sniper rifles exclude the feature. That is because the extra gas needed for the slide or bolt operation reduces the potential range of the bb in a sniper rifle, and hence reduces accuracy over distance. So electric or nonblowback gas for sniping, electric or spring for gaming, and gas for authenticity. Gas powered Airsoft guns offer a number of advantages and disadvantages, but when assessing their pros and cons it is likely best to consider your purpose for buying one and then decide which type best suits your needs. There are no doubts whatsoever that gas power offers a gun that looks and feels like the real thing in use, but that blowback reduces gas life, particularly in full automatic firing mode.