Trent, do you have or can make a jig to measure inside case wall thickness about 3/4 inch from the base of the cartridge case? A company in Calif used to sell them, neconos.com. For the difference to be really evident, you need to have loaded the rounds to a tenth of a grain of powder. The bullets must exit the barrel at the same velocity.

I made a wildcat cartridge from Winchester 300 savage brass and it sorted awful. Only about 10% was even useful and the best of that brass was the worst of the Lapua.

I could make an offset rod that would mount to my RCBS case master. I'm not sure that device is accurate enough though. I imagine you are/were using a micrometer huh?

You could make the device. All you need is a ridgid ball anvil to slip the case over and a v cut block to let the base of the case ride on. Then mount a dial indicator just above the anvil. When you rotate the case by hand, it will indicate the case wall thickness. I always marked the thickest point with a magic marker and later filed a notch in the rim. I considered cases with less than .001 as match cases but I still marked the thickest point. Each time you fire the brass, the cases keep getting worse.

Look at the website and you can see a photo of the device I have.