[Jchoi]

Which cylinder head did you end up using?

Originally Posted by Maximus

Had a similar issue with my VFC Calibur recently. Was doing it with Lonex and Stock hopup, every mag I tried, even high caps.

In the end my problem turned out to be a loose air nozzle. If I took off the upper to expose the gearbox and the air nozzle, i could put my finger on the nozzle and it would move up and down and left and right about 1mm, lots of play and i'm not talking about it sliding back and forth. What was likely happening was the BB's from the mag were pushing the air nozzle up from the spring tension and not allowing it to align to the bucking.

Solution was to replace the Cylinder Head (not the nozzle) and add a stronger tappet return spring. On the new cylinder head the air nozzle would slide gently and absolutely zero wobble up/down or left/right.

To see if this is the same issue for you, sounds like it is, because once you go through 30 or so BB's the spring tension is significantly less and doesn't push up on the nozzle as hard. Take your upper off and just feel your air nozzle. It shouldn't have any play in it (up/down especially) what so ever.