as you pull the trigger the hammer is released and the gun is fired. continuing to pull the trigger activates the 4-way(3-way whatever you wanna call it). in fully pulled trigger position the bolt is open allowing a paintball to drop in. as you release the trigger the bolt returns to its 4ward position and is again ready to fire.
I too am interested in making either my pgp or another sheridan pump semi. i think i have decided to get it done by punishers. the autocrapper has the 3 way on the outside which i would stay away from. if you are able to buy a 4way grip from punishers. $150.00. but thats not in everyones budget.
a problem i ran into is understanding the rock regs job. i know it lowers pressure for the pneumatics but to the rest of the gun too? help from neone would be helpful