Once again a heartfelt thanks to everybody for chiming in, especially Bohonkie up there. Much like yourself I'm not sure if it was the polishing itself or if it just gave it the deep cleaning to end all deep cleanings, but took the old M&P out to the range today with an assortment of non-Plus P specials ranging from lead wadcutters by Remington, to HPR, Winchester FMJs, and even some musty old cowboy reloads I had sitting around. Ate every one like a champ; but more importantly after that polishing slid out every spent shell like silk, regardless of brand or load. Superb accuracy at 15 feet and no evidence of key-holing, so I am once again a happy shooter.

Happy new year to everyone!