Quote Originally Posted by Idaho View Post
biged, you posted this pic early on in this discussion and it is quite telling and much appreciated. This issue has not cropped up for me before with either Lapua or LC brass. This batch was Starline so I will have to watch to see if it is just related to the type of brass or if it was because I tumbled it too long. Thank you very much for your input.
I have found this happening mostly when I tumble annealed brass that has been trimmed and chamferred. After annealing it is relatively soft compared to not and after trimming and chamferring, the mouths are pretty thin at the edge and will peen easily.