...I am getting a new breech seal from Crosman for my Venom as the top half is flat.http://www.crosman.com/cs/manuals/crosman-rifles
How "complete" is the loss of power? Scotty
On some of the gas pistons there is a problem that the piston has side movement in the cylinder piston which causes premature failure of the gas piston. Airgun Toys I do believe has a shim or sleeve to keep the gas piston centered. As for the breech seal shim you may try dental floss.