In the interest of simplicity, we're going to talk about how a co2 powered blow-back style paintball gun works, because an electric paintball gun has so many complex parts, each one could have it's own explanation. so, Simply put, a co2 tank is screwed into the back of the gun, the gas flows through the gun, and is used to move the bolt back and forth, creating enough pressure behind the ball so send it flying out of the barrel. So, since this style of paintball gun is mainly gas through (no air regulation between the tank and the rammer), the main part that must be explained is the poppit valve. When pressure from the gas is released into the lower chamber when the trigger is pressed, the rammer is compressed back against the spring, moving the bolt backwards and allowing a paintball to enter the upper chamber the bolt then slams forward into the ball, followed by a puff of gas which propels the ball out of the barrel at about 300ft/s.the force from the gas being released again pushed the rammer back, compressing a spring, which will then repeat the whole process over again as the trigger is pulled again. This is where the type of paintball gun gets its name of "blowback style" as the gas released with each trigger pull "blows back" the rammer into place, resetting it and preparing it for another shot without the user manually having to move anything between shots.