[Dynamo]

if you are using the hopup sleeve that came with the pro-win, replace it.
also it wouldne be a bad idea to replace the spring on that little ramp thing with a stiffer one (it will stop multiple feeds).

the opening on the hopup rubber is too narrow, so its only letting BBs through once the air pressure from the cylinder has enough force to push the BB through the hopup opening. once the BB does make it through, you already lost most of the air from the cylinder.

the pro-win hopup opening is so narrow it can have enough pressure to stop the nozzle from pushing the BB forward.