Understanding CO2 as a Propellant

CO2 has been powering air guns for quite a while, going back to Paul Giffard in the 1870's who used the gas as a propellant for his guns that were sold to galleries back in the day. The gas has unique properties that lend themselves to being a very effective means of making an air gun, or in this case, a gas gun, work like it should.

CO2 has the ability to transform from a solid straight to a gas, without going through the liquid phase. Remember dry ice? Well, there you go!

Under pressure, CO2 becomes a gas over a liquid. Inside the powerlet that we are all familiar with, you have a gas and a liquid. CO2 is very temperature sensitive, and when you shoot, some of the gas is used to propel the pellet. At the point of firing, as the gas is released, some of the liquid is changed to gas to once again regulate the pressure in the container in which it is found at that specific temperature. If the temperature remains constant, the pressure from the CO2 will be constant until the excess liquid is boiled away, at which point the velocity of the pellet will begin to drop dramatically. That is one very useful feature of CO2 in that you don't have a large deviation in velocity from shot to shot as long as there is a supply of liquid CO2 still in the container.

Since CO2 is a refrigerant gas, it produces a chilling effect with each shot of the gun. In a single shot, this isn't all that big a deal since the time you take to reload allows the CO2 temperature to rise once again to its surroundings. However, some guns feature a rapid fire feature, and if you fire off several shots in a row, you will notice a lower velocity as the gun rapidly cools, thus affecting the power you get from the expanding CO2. Rest just a moment, and the velocity will return to a more even level.

If you have a CO2-powered gun, then know that the seals in the gun are the parts you should be careful with. Without them, your gun won't hold gas. Nick a seal, and a slow leak will rob your gun of gas. Rupture a seal, and you might as well throw the gun at your target for all the good it will do you.

In very warm weather, some CO2 guns will lock up, refusing to operate. This is because the pressure, dependent upon temperature, is too high in the gun for the valve to open. Take it inside for a short time to cool off, or stick it in the refrigerator for a few minutes, and your gun will once again function. Conversely, try to hunt in cold winter weather with a CO2 gun, and your power level may not be up to the job you are asking of it because the ambient temperature is so low.

CO2 guns are fascinating and lots of fun. Crosman made many types of CO2 guns, starting after World War II, and pretty much started the CO2-air gun craze. As their guns gained popularity, the 8 gram CO2 cartridge gave way to the 12 gram version. It is the standard today that most CO2 airguns use that don't run on bulk gas.

I own several CO2 guns, from the Crosman 2240 to the Tech Force 78, a copy of the Crosman 160. They shoot wonderfully, and are loads of fun. It is so easy to just install a powerlet or two, and a pocket full of pellets supplies me with many shots for hunting or plinking. So if you haven't delved into the wonders of a CO2 air gun, browse through Compasseco's website and check out the offerings that are found here. You will find several guns that use that wonderful gas, CO2!