I just ordered a new breech and piston seal .. tissue test ? If I understand correctly put tissue over breech and if it blows it off there's a leak??? Iv been researching this and I'm totally willing to take it apart deburr / polish and all that , but can't find any good info or videos on how to do it.. I'd also like to see about swapping out that 25mm piston and putting in a 33mm ,just an idea for now if anyone has done that conversion or has any ideas I'd like to hear about it ...
Well there are remnants of a seal, check the compression tube and sear for galling. I recently fixed a Gamo Mach1 for a friend and there was metal breaking loose from the sear and galling the compression tube and tearing up the seal, and his seal was still sorta OK looking.