[Flatlander]

Have you tried the flashlight in the hopup while looking down the barrel trick so see if the nozzle is sealing on the rubber?

I've got a similar issue with my SPR but haven't had time to completely fix the problem yet due to school. I've got it narrowed down to an alignment problem of sorts. The nozzle isn't always sealing with the hopup rubber - I can distinctly hear when it is (gives a nice low thud sound) and when it's not it has a high pitched snap.

Anyways, as buddy found that his modify gear axles were thicker than the stock ones so his tappet plate sat further back than it was supposed to - therefore the nozzle could not travel forwards enough to seal with the rubber. He filed down the tappet plate fin slightly to compensate for the larger axle shafts.

Hope that helps. Good luck, Tys.