Half Cycle when shooting

OK. My friends JG Beta Spetsnaz AK has a problem. He describes it as:
"The piston puts the BB halfway in the chamber and then it's like it doesn't have enough power, but I know it does."

By this explanation, I thought that the problem may either lie in the air nozzle or the tappet plate, however I'm not a very experienced tech and I would like some advise as to what it might be.

Thanks in advance, Accordion Kid.

[quote="Accordion man"]OK. My friends JG Beta Spetsnaz AK has a problem. He describes it as:
"The piston puts the BB halfway in the chamber and then it's like it doesn't have enough power, but I know it does."

By this explanation, I thought that the problem may either lie in the air nozzle or the tappet plate, however I'm not a very experienced tech and I would like some advise as to what it might be.

Thanks in advance, Accordion Kid.[/q]

Could be a few things, maybe his hopup is just messed up to the point where it won't feed. Air nozzle is not providing correct air flow. Cylinder head and piston could be broken thus ruining air seal and making for a less powerful air burst. It's most likely the cylinder head and piston