As far as case stretch goes, smoking a fired case and setting the resize die as Eldeguello suggested should take care of the problem.
As far as the dimpled case goes, from what I got out of the original post, the case was NOT dimpled before firing due to the die being set excessively low. If this was the case, all or most of the cases would have exhibited it before firing. The dimples appear to have occurred in the chamber upon firing and the case rupturing.