Bought a Gamo in .177......man am I pissed. First shot went off like the spring was broke. I oiled up the o-ring around the breech and the next shot went off like a .22. Then, sppproinnnggg again. Store said they can't take back air rifles, call manufacturer. Anyone have the same problem and may I ask how it was fixed? Thanks in advance.....there's a groundhog waiting for an answer.