Do you clean the barrels before use. A lot of Gamo’s are made in China now and from experience they use a lot of barrel grease to preserve them. So imho you’ll get a far better result after a clean. I always clean my brand new guns. Even my Weihrauch HW98 and 95k needed a good pull through clean, now they are pellet on pellet at 25 metres ( bench rested ) just some advice