I was cleaning 30-30 brass and found this FC case. Looks like boolits from a cold or oily mold.
I have included 5 photos rolling the case to the left in order to show all of the disfiguration. I marked the case with a sharpie to show how much of the case is disfigured. The arrow on the length wise line points toward the wrinkled area.
I have seen similar appearance on cases which were fired with some sort of trash in the chamber. It appears to have been made this way.
In the first pic look at the neck above the arrow.
#2 neck and just below shoulder.
#3 " " " " "
#4 " " below shoulder to about middle of case body
#5 shows (between the lines) portion not disfigured.
Have you ever seen this sort of defect in brass.