Pressurized carbon dioxide tanks are the most commonly used propellant in the paintball industry today. While the number of shots a particular tank size can provide differs based on the gun used, expect 40 to 45 shots per ounce. Even more important than tank size, however, is the type of tank used, i.e. disposable vs. refillable pin valve.
Known as “cartridges,” disposable tanks hold 12 g (0.4 oz.) of liquid carbon dioxide. Extremely portable, cartridges are sold in packages of 10, 15, 25 and even 100. Although you’ll have to replace them more often during game play, disposable tanks do not require a filling machine on-site. Disposable cartridges in 3-oz. and 4-oz. sizes are available but they cost considerably more than the standard 0.4-oz. size.
In general, disposable tanks are better for pistols or semi-automatic guns with a relatively low rate of fire.
Refillable Pin-Valve Tanks
Sold in 4-oz., 9-oz., 12-oz., 16-oz. and 20-oz. sizes, pin-valve tanks are easy to maintain and inexpensive to have refilled at most paintball stores or fields. Because of their larger sizes, refillable tanks are the best choice for automatic guns. Depending on the size of the hopper (the bullet magazine) you use, a 12-oz. tank could allow you to fire several hundred rounds within seconds.
However, if you do purchase a high-capacity pin-valve tank, you should also purchase a part for your gun called an “expansion chamber.” The low temperature of liquid carbon dioxide can make the O-ring seal between the tank and the gun brittle over time, leading to gas leaks and low pressure. An expansion chamber allows the liquid CO2 to evaporate into pressurized gas before even reaching the O-ring.
Pin-Valve Tank Safety
A damaged O-ring seal isn’t simply a nuisance; in some cases, it has actually proved deadly. If the O-ring fails completely, a 12- or 14-oz. tank suddenly becomes a missile traveling at hundreds of feet per second.
Therefore, be sure to have your tanks professionally hydrotested every few months. If the tank gets any scratches or gouges during a game, make sure it gets hydrotested before refilling it or playing again. CO2 tanks also feature a hydrotest expiration date stamped on the side; do not use the tanks past this date! If you decide to buy a used tank online, make sure that you request to see a picture of the tank’s expiration date stamp.