I just got a Hatsan Flashpup Synthetic in .25 today and spent a few hours with it this afternoon testing pellets, adjusting the trigger, zeroing in with the best pellet so far, etc. Pretty quickly in the process I noticed a puff of air hitting my right hand (trigger hand) with each shot. So, I investigated with tissue paper and found the air coming out near the trigger. I took the gun out of the stock and continued my investigation. I found what appears to be a vent in the Quiet Energy shroud. You can put a piece of tissue on this vent and fire the rifle; the tissue goes flying.
After watching a video about removing the QE shroud I think I understand. The air the QE system strips off has got to go somewhere. There doesn't appear to be any vents at the front of the QE system so I am assuming this vent hole (which is underneath the stock) is where the pressure is relieved. Apparently its supposed to be this way. I initially thought I had some kind of leak but there are no fittings in this area - all that is back near the rear of the stock. And, my energy and velocity is about what I'd expect with 26.54 gr Hades pellets (average 827 FPS with an average of 40 FPE).
So - Hatsan QE owners -- can you verify that this makes sense and is indeed what is happening?
Here's a pic of what I assume is a vent:
