Paintballs are extremely fragile so firing them down field at 300 feet per second is not an easy task. Despite this we do it all the time. If you look across the wall at a paintball store you will see a wide selection of guns that do this in multiple ways, but at their core they all work the same way.

Much like the first paintball gun, all modern paintball guns used compressed gas to fire a paintball. If you have ever shot a spit ball out of a straw it is the same concept, compressed air behind the ball pushes it out a tube. That’s the simple answer but if you want a more in depth explanation read on.

Picture of a Nelson paintball gun
An early Nelson Nel-Spot, the first paintball gun.

Under Pressure

At sea level the air pressure in the atmosphere is approximately 14.7 pounds per square inch (psi). When we compress gas it wants to expand until it has reached an equal pressure with the atmosphere. Paintball guns have an air source that is at a higher pressure, often as high as 4500 psi. We regulate this air down, often through two stages of regulators, down to 100-800 psi. This is guided into the firing system inside the gun. When you fire the paintball gun it allows this air to expand behind the paintball which offers very little resistance so rather than going around the paintball it pushes the ball while the gas expands.

How paintball guns move the air from the air source to behind the paintball is what varies from marker to marker. The volume of air, speed it is released, and how high the pressure also varies. For more information on how different paintball guns operate stay tuned for an article on different operating systems that I will link here.

Etha diagram
The diagram the the Planet Eclipse Etha manual

A note on barrels

The use for expanding gas is also why different barrel bores have such an impact on efficiency and consistency. If the barrel is smaller than the paint less air can escape around the ball allowing for less air to be used. A larger bore will allow more air to escape meaning you need to use more air. Both of these options are very consistent compared to a “perfect” bore match. We did a whole article on barrels already but I like to reiterate this as often as possible with how much misinformation is out there regarding paintball barrels.