[Jaaks]

Are u using a soft or hard hop up rubber? because I'm having the same issue and I"m gonna switch to a hard hopup rubber which should not affect the bb's as much as they leave the barrel. I was told the reason behind it but I cant remember how to explain it well but give that a try.

The spring is useful as well to make sure the hop up unit is sitting flush against the mechbox so that there is no air loss.