I recently acquired a G&G v.2 gearbox and I took the trigger return spring from it to fix my other gearbox. I am thinking about rebuilding his gearbox for outdoor use. How good are the stok parts? I was checking for compression and I think I need to replace the o ring on the piston head. Gonna redo the wiring as well. How reliable is this gearbox. Any opinions are appreciated. Thanks!