Every paintball gun needs some way to be powered in order to fire a paintball. There are 2 ways to go here and you should pick what is best for you. One way is the easiest and cheapest, which is using CO2. CO2 is a liquid that expands to a gas, and it is that gas that your paintball gun uses. The Pros of using CO2 is that the up front costs are cheaper as tanks can range from $20-$50. You can usually get quite a few shots of a smaller tank too and filling your CO2 tank is as easy as going to your local paintball field or paintball store. The Cons of using CO2 comes down to performance. When it is cold outside, the CO2 tanks tanks longer to expand to a gas which can seriously effect your consistency. As you shoot through a whole tank, your velocity can keep changing. Even if you let your paintball gun sit for awhile, the heat can cause your velocity to spike. These fluctuations can cause inconsistent velocities. This correlates to your range changing with every shot and your accuracy up and down will be effected. When it is humid out, the CO2 will be visible as it exits the barrel which makes it harder to see where your shots go.
The next option is using an Air Tank. These are also commonly referred to as Nitrogen Tanks, Compressed Air Tanks, and HPA (High Pressure Air) Tanks. These are all the same thing. Compressed air is made from a compressor while nitrogen is pulled from the air and compressed. Nitrogen is mainly utilized in welding, but can be used for paintball. Mainly what you see across the US is compressed air as many fields and stores now have compressors. The Pros of using an air tank is mainly performance. The consistency from shot to shot and through out your whole tank is extremely good. The first time I went to an air tank, I shot half a case of paintball because I could not believe how much more accurate it was over CO2. The orings on your paintball gun will also last longer as the cold of CO2 effect them more and makes them deteriorate faster. Since air tanks are compressed air, you can use a gauge to see how much air is left. Filling an air tank is also much quicker and easier. The Cons of air tanks is that the up front costs are much greater and filling can be more difficult as there are still many stores and fields that cannot fill them. Make sure to check with your local paintball places to make sure they can fill them before you purchase one. If you have been using CO2 for a long time, switching to an air tank will be a huge upgrade and you will be blown away by the increase in accuracy as I was.
