Carbon Dioxide vs. Nitrogen
Which gas do you want in your gun?
When it comes to powering your paintball gun there are two basic ways to do it - with carbon dioxide (CO2) or with nitrogen cartridges or tanks. However, some companies, such as Tippmann, are now making propane-powered guns. Newcomers to the game may not know the difference, but experienced players usually have a preference.
Carbon dioxide turns into liquid when it's compressed, but it has to expand to a gas when it's used to power a paintball gun. This procedure requires energy, which causes the tank to cool as heat is used to turn the liquid CO2 into gas. One downside to CO2 is that if you're constantly shooting your gun, the tank can get so cold that ice crystals can form on it, especially if it's cold outside. If the CO2 container doesn't have an anti-siphon tube on it, or if it's shaken while you're shooting, the liquid CO2 could enter your gun. If this happens, the liquid will travel through the gun instead of the tank and it will evaporate and freeze the gun. The next time you shoot, you'll see clouds of CO2 vapor coming out of the gun. This is referred to as "drawing liquid", and it will damage the gun's internal seals and o-rings. The gun won't shoot again until it warms up, which could leave you right in the line of enemy fire with no protection.
There is also a downside to CO2 and heat. You should never leave a tank sitting in the sun, as the heat can make the gas to expand to a dangerous level. The tanks do come with safety valves in them, but it's still better to take extra precaution. If you're firing shots off in rapid succession, gaseous CO2 is used up. The liquid CO2 takes time to evaporate and rebuild the internal pressure. This could create a big difference in the gun's velocity, accuracy and range.
Nitrogen (N2) or high pressure air still remains a gas when it's compressed. When it expands, it will also cool the tank, but it does it a lot slower than liquid CO2 because it doesn't have to change from a liquid to gas. Because nitrogen doesn't have to go through a transforming process, the pressure doesn't change much when firing in rapid succession, and the gun is more accurate than it is with CO2.
However, nitrogen is stored at a higher pressure than CO2, and the nitrogen and HPA tanks cost more and are heavier. Newer tanks are often wrapped in composite materials, which allow for thinner walls and lighter weights, while withstanding greater pressure. Nitrogen tanks can be filled with pure nitrogen or compressed air and these sources are usually used by people who play quite a lot of paintball and have top of the line guns however, they're becoming quite popular among casual players these days. HPA tanks can be filled with both nitrogen and compressed air, but can't be filled with CO2.
HPA, which is 79 percent nitrogen and N2, is preferred by some players as it's easy to fill the air system from a conventional scuba tank. Some players prefer N2 instead of HPA as the oxygen in the HPA can corrode their guns.
Conclusion: It's a toss up! N2 is generally preferred by paintball players over CO2 as it won't liquify and leak into the gun. The solenoids on electronic guns are quite sensitive to this, and some manufacturers will specify to use only nitrogen or HPA. Nitrogen will also usually give you a more precise and consistent shot than CO2, especially during rapid firing. However, CO2 tanks are quite a bit cheaper than nitrogen tanks. You can also buy accessories - such as anti-siphon valves, expansion chambers, regulators and remotes - to help stop the liquid CO2 from entering the marker, but that will cost you some more money.