This page is an attempt to answer questions about two of the most commonly purchased, and often misunderstood accessories for paintball guns.
 
 

What is an Expansion Chamber?
An Expansion Chamber is a device attached to a paintball gun designed to reduce occurrences of liquid Co2 getting into the valve area. Expansion Chambers accomplish this by routing Co2 through a passage or series of passages, which allows liquid an opportunity to boil, or expand into gas.

When do you need an Expansion Chamber?
The introduction of liquid Co2 into a valve system can cause pressure fluctuations which lead to velocity spikes. This occurs most frequently on paintball guns which use a "bottomline" set-up. Since liquid Co2 follows gravity, the horizontal orientation of the bottle in combination with the various angles at which the gun is held by the user allows the erratic introduction of liquid Co2 into the system. Any gun suffering from this problem can benefit from an Expansion Chamber, although like any anti-liquid system it is not always 100% effective.
Since remote lines serve a similar purpose and are most often connected to bottles in a vertical position, guns with remote Co2 set-ups may see no real advantage from the addition of an Expansion Chamber. As in other cases, an Expansion Chamber should only be used in remote systems that are experiencing continued problems related to Liquid Co2.
Guns using HPA (High Pressure Air, a.k.a., Nitrogen) as a power source do not need an Expansion Chamber since the entire "liquid" issue is nonexistent.

What is a Regulator?
A Regulator is a device which controls the output pressure of the gas power source on paintball guns. The Regulator can only maintain or reduce the pressure of the gas coming from the source tank - It cannot increase the pressure. Aftermarket, or on-gun Regulators are adjustable through a certain pressure range as determined by the manufacturer - not all Regulators work with all paintball guns. For example, some Regulators are adjustable for 0 to 600 psi, which would negate the use of the Regulator with a gun requiring more than 600 psi to operate.
Co2 tanks are generally not sold with built-in Regulators, all though several companies manufacture replacement valves which include a built-in Regulator. For most Co2 powered paintball guns, regulators are placed in the gas line somewhere between the tank and valve.
All HPA tanks have a built-in regulator, since tank pressures are 3000 psi and above, which far exceeds the operating requirements of any paintball gun. The built-in tank Regulator is often used in conjunction with an on-gun secondary Regulator, especially in cases where the tank Regulator is not adjustable.

When do you need a Regulator?
Anyone wanting to control the pressure at which their paintball gun operates needs a Regulator. Whether Co2 or HPA is the power source, there are numerous advantages to controlling the operating pressure of paintball guns such as maintaining the consistency of the velocity, and more finite control over velocity adjustment. There are also some advantages to operating at lower pressure, which requires a Regulator.
A Regulator can also be used to help eliminate the erratic introduction of liquid Co2 into the system. Since liquid Co2 exist at higher pressures (at a given temperature), the lower the operating pressure, the less likely Co2 will exist in a liquid form. Like the Expansion Chamber, the Regulator alone will not totally eliminate liquid Co2 and should be used in conjunction with another device, such as an anti-siphon tube in the Co2 tank.

Should a Regulator and Expansion Chamber be used together?
Depending on how the system is set-up, a Regulator and Expansion Chamber can be used together, but in most cases, the use of both devices is excessive.  More likely than not, the combination will adversely affect performance.
An Expansion Chamber can be used to help eliminate liquid Co2 before it reaches the Regulator, but is more cumbersome than other methods such as the use of an anti-siphon tube in the Co2 tank.
A set-up where the Expansion Chamber is placed between the Regulator and valve system may partially negate the effectiveness of the Regulator, since it allows the regulated gas an opportunity to warm and expand. Such a set-up is also unnecessary in a properly organized system, where efforts should be made to eliminate liquid Co2 before it enters the Regulator.

Which is better, a Regulator or an Expansion Chamber?
With price not being a consideration, a Regulator far outperforms an Expansion Chamber. While offering the same anti-liquid advantages, the Regulator also offers actual control over the operating pressure of the paintball gun. An Expansion Chamber should only be considered if liquid Co2 is a problem, and a Regulator is outside of the user's price range.

Regulator vs. Expansion Chamber vs. Vertical Bottle
The following test was conducted using a stock Avalon Diamond GT, which is a two-tube blow-back paintball gun. The purpose of the test was to check the differences in velocity consistency when using a standard vertical bottle set-up, a 6-stage expansion chamber, and a regulator. Every effort was made to keep the parameters as close as possible during the test. The three steps of the test were performed back to back, using and the same brand/batch paintballs. A standard 12 ounce Co2 tank was used (no anti-siphon tube), and both the expansion chamber and regulator were used in the vertical bottle position, and fed from a standard bottom-line adapter secured to the grip frame.