I put it back together eventually and lubed everything generously. The piston's screw was tight, as it was loctited by ILLusion himself when I purchased it from him. I test fired 3 mags each with 7 BBs each, and it still has the same problem. Since I cleaned the upper assembly, the slide racks back super smooth and there's no more roughness in the nozzle's forward and back motion either. I still have no idea what the problem is. If its a mag issue, then I don't know what it could be.
Do you have experience with KM high flow valves?
The ultimate measure of a man is not where he stands
in moments of comfort and convenience, but where he
stands at times of challenge and controversy.
- Martin Luther King, Jr.