When it says that an expansion chamber kit helps you fire more balls and is gas efficient does that mean that less gas is used to fire the paintball resulting in lower BPS or does it help prevent gas from escaping? Also, what does it mean when a valve is running on low pressure? Does the balls firing distance decrease? Where is the valve located?
Well, being able to fire more and being more gas effecient is the same thing.
CO2 is stored as about 2/3 liquid, 1/3 gas. The 1/3 gas helps the 2/3 liquid transfer from a liquid to a gas. This is why CO2 tanks are measured in weight.
An expansion chamber helps the liquid CO2 expand (hence the name) and when something expands something becomes larger. Gas has the fastest moving molecules, liquid has the second fastest, and solids have the slowest. So, no. Lower gas used does not mean a slower rate of fire.
A valve running on low pressure means that the valve uses less pressure than usual to operate. This does not mean the velocity will decrease. A good math expression for this is Velocity = Pressure x Mass. In order to keep the velocity good you need to balance out the two. The valve is usually located on the lower tube of paintball markers.
an expansion chamber (x-chamber) allows C02 more room to expand before it enters the valve of your marker. The room allows the gas to flow more consistant.
A low pressure valve uses a low pressure gas, such as nitrogen, to work. (i think)