[nijwnfi]

Without looking at the rifle, sounds like chamber needs cleaned out. Get some automotive brake parts cleaner and soak the chamber. That dissolves cosmoline like crazy. Are you shooting lacquer coated steel case ammo? In a tight chamber this can cause sticking also. Brake Cleaner will work for both. Oil lightly afterwards. I also use this to clean the gas piston and tube. Oil very lightly afterwards, then wipe it down well, gas system parts should be dry. That's the easiest cheapest thing to try at this point.