My various 7mm mags love very warm loads where they shoot sub 3/8" groups. 100 new cases per new barrel, throw the brass and the barrel away at the same time, start over. After having Lot# of new brass Rockwell tested, brass hardness in some brands will vary 6% over the lot#. So, I know that the soft brass will loose primer pockets, which is to be expected. Soft brass in the Lot# will also develop a ring from case stretch first. I De-Prime with a Hand de-priming tool, throw away brass without much thought when they feel loose. This step saves you from case prep plus priming to find out that the primer pocket is loose where I have a tendency to not toss the case.
I carefully adjust my sizing die down so that the bolt closes easily. Whatever the shoulder set back is what I am forced to live with. I also expect to see the "ring" around the case on the softer brass, which is an indication of case stretch. In the 40 years of shooting the 7 Rem mag, I have only had one actual case head separation, and that was easily removed from the chamber with a 45 caliber pistol cleaning brush. Unless you are blind, the ring around the case is very, very evident prior to a case head separation.
I have found that my Remington, Browning, Savage, and Custom 7 mags shoot their very smallest groups on Full length sized or partially full length sized brass vs Neck Sized brass. On the neck sized brass, I had to lower powder charges(velocity), and I could not run the loads at peak pressures where the accuracy was found to be the very best.
Mismatch dimensions on dies, new brass, and chamber reamers can be a real mess to deal with.