I've had my demon for about a month now and have only shot it twice. The two times I used it, it was a great marker. I'm about to sell it and went through everything in the marker making sure it was in working order but when I aired it up, I could hear a small leak coming from where the grip frame meets the body. I changed all of the orings on the bolt thinking it was that but I had no success. I'm wondering if anyone knows what this possibly could be.
I'm not totally familiar with the demon since I don't own one but remember it's a gas through system. Any orings that seal the air passages in the body of the gun also have potential to leak. There is one such oring between the grip frame and the upper body if I'm not mistaken.