I guess it is something else then. I took great care to make sure they were aligned with each other when I re-assembled it. I figured it was not tight enough against the transfer port of the valve. Maybe I just totally messed up the pumping mechanism all together. Like you said though, wrong platform for mods. Worked great out of the box putting out RWS Hyper Velocity at well over 530 fps. As far as construction goes, way too flimsy.