How Paintball Works | HowStuffWorks
In the last section, we saw that paintball guns propel paintballs with a quick burst of compressed gas. In the animation below, you can see how this process occurs in a conventional pumpaction gun.. In the middle of the gun, there is a long valve runs from the barrel, where the paintballs are loaded, to a chamber at the back of the gun, where the gas cartridge is connected.