If you're experiencing peening of the cartridge case mouth, did you try increasing the amount of tumbling media, or decreasing the number of cases? As you load and start tumbling your cases, media moves into the cases and is not available to cushion the cases from banging into each other. The secrete is to find the best balance of water, media or size of media, cases AND tumbling time. Sometimes less is more when it comes to tumbling time.

As for the burr problem that cropped up, sounds like you have a very tight "no neck turn" chamber. Like you, I anneal and go through the whole clean, trim, chamfer cycle about every third time for my 6BR.

For my bolt action 223's, I only neck size and never get more than a slightly snug chambering round. Almost never trim, or anneal, and still shoot sub half minute groups, but I'm not a competition marksman.