After shooting alongside muzzleloaders, I confess that I now gauge the ventholes in my brass - amazing variance. I use the chuck-end of a drill bit and roll the brass on its side. Wheather that brass is new or used, you'll find that the bit will stand proud in some brass (new or used) and virtually flop out of others. Couldn't convince me that that wouldn't affect shot-to-shot performance. I group my brass by this test.