You are right in not wanting to "over polish" the chamber, the possibility always exits of changing it either by enlarging it in an area or getting it somewhat "egg shaped" if you polish one area to aggressively and for to long. What I would also suggest is disassembling the ejector itself and lightly smoothing and polishing disassembling the surfaces, especially any bearing surfaces. Just take it apart, look at it, figure out how it works and where the parts touch and go at it. When you are done, clean, dry, reassemble and lightly lube with a non oil substance and hopefully it will be what you need. This has been touched on before and spoken of but I did not see anything about it in the FAQ's...best of luck....<><....
of course, someone who was prepared for all contingencies would also have either have a notch in the breech end of the barrel AND a small screwdriver or knife, OR a piece of cleaning rod or metal rod (end of a broken drill bit) to drop down the barrel....<><....