[Deathfox]

its not because of a tightboar barrel.... You only have a 366mm barrel, you wont have problems until u get larger tight boars like 510mm.

But its more than likely your hop-up rubber. I would be willing to bet money on it. BUT if you try a new rubber and if its still isnt were you want it to be, stretch the o-ring on the piston head. Sometimes they come a little shrunk and messes with the seal in the cylinder. But i doubt its that. its the hop-up rubber