Trying to get consistant velocity from an inconsistant power source

The Mag Chamber Advantage
This has been a problem faced by paintgun designers and airsmiths from the beginning of the sport of paintball. The problem is rooted in CO2 as a power source.

Carbon dioxide can be very efficiently stored in a gas over liquid form. In this form, as gaseous CO2 is used by the paintgun, it is replaced by more gas which boils out of the liquid CO2. Vast amounts of CO2 gas can be stored in a very small space when converted to liquid, so this makes CO2 an excellent power source in terms of energy stored versus size of the power supply, or to put it in the way that matters, the number of shots per fill of the tank.

The problems:
One of the first problems discovered with the use of CO2 was that of liquid CO2 getting into the valves of the paintguns. Intermittent feed of liquid into some paintguns will cause large variations in velocity, other guns will simply cease to function, due to freezing of their internal seals.

Another problem is inconsistency in pressure. As the liquid CO2 boils off into gas, it cools down, absorbing heat from its surroundings. Naturally, it absorbs heat from the gas that has just boiled off. Since the pressure of a gas is variable with its temperature, this lowers the pressure of the gaseous CO2. This fluctuation in pressure translates to a fluctuation in paintball velocity, which in turn affects the accuracy of the paintgun.

Enter the solutions:
There are a number of solutions to the CO2 problem, each with its own pros and cons.

Regulating CO2 is one solution. The paintgun is set to operate at a lower pressure than the CO2 tank is providing, and a regulator steps the tank pressure down to the new operating pressure. This works well, and provides a more stable gas pressure than straight CO2.

Its weak points become apparent when the paintgun is fired rapidly enough that the CO2 chills to a pressure lower than the regulator's setting. Then the pressure to the paintgun is lower, and the marker experiences velocity fall-off until the gas in the tank warms up. Another problem that arises during rapid firing is that cold CO2 gas can go past the regulator at the correct pressure. If the paintgun is not fired for a while, that gas can absorb heat from the paintgun, until it is back up to the same temperature as its surroundings. In doing so, its pressure will rise, and so will the velocity of the paintgun. This can lead to chronograph penalties, or worse, depending on how great the fluctuation.

One of the earliest solutions was the expansion chamber. In the better expansion chambers on the market, you will find two features. First, they are vertically aligned, with the input near the bottom and the output near the top. This ensures that any liquid CO2 which enters them falls to the bottom and can not splash up into the valve. Second, they feature rapid heat exchange, and high heat capacitance. When gas or liquid enters an expansion chamber, only one thing can make it expand, and that is heat. If the CO2 in the chamber is below the outside temperature, it needs to absorb enough heat, as quickly as possible, to bring it up to the surrounding temperature. Once the temperature is stabilized, the pressure will be as well. The material of the expansion chamber is important. Aluminum is an excellent conductor of heat, and has become the accepted standard for expansion chambers. The more metal that makes up the expansion chamber, the more heat it can rapidly exchange to the gas inside. Thermal transfer engineers refer to this as heat capacitance. Also important is the external surface area of the chamber. The more area, the more heat it can absorb from the outside, to replace the heat it is dumping to the gas inside.

The Mag Chamber - going one step further:
The Mag Chamber from USA Performance Products goes one step further in expansion chamber technology. The Mag Chamber is vertically aligned, and it aligns the CO2 tank vertically as double protection from liquid CO2. Instead of limiting itself to the external area of the chamber for heat exchange, it uses the entire body of the Viper-M1 as a heat exchanger. TheViper-M1 and the Mag Chamber are heat treated to become one single piece of T6 hardened aluminum. As one continuous piece of metal, theViper-M1 can exchange heat through its entire body, and transfer that heat to the waiting gas in the Mag Chamber. This allows for very rapid temperature stabilization, and combined with the Viper-M1's pressure compensating valve, provides an extremely stable velocity, with the cost, size and benefits of a compact gas over liquid CO2 supply, and none of the mechanical complexity of regulation or compressed air systems.