Had a friend with scratched chamber in a used gun he bought. Would not eject. Had to drive the empty out with a cleaning rod. We took a dowel and slit the end and inserted a piece of crocus cloth. Spun it with a drill till it would eject. Took a few rounds but he's had the rifle for years and no more problems.
Fred
Roy Dunlap wrote about that, it works. Have done that with worn 400 wet-or-dry. Doesn't get rid of the scratch, polishing not grinding, but does something like break the edges of the scratch (I guess) so brass doesn't grab. Works for surface rusted/crudded chambers in balky semiautos too.