My boy's 20 gauge was jamming on every round. Took it to the local gun smith. He showed me a ring about 4" into the barrel from the action, that he said was small particles of was plastic that had burned onto the inside of the barrel. He said it was grabbing the empty shells and not letting them eject.

He recommended I get some solvent and scrub it out with that and a wire brush from my cleaning kit.

An hour and one sore shoulder later, it is still there, melted in the barrel.

Anyone ever had this, and how do I get rid of it?

Thanks.