I buy brass in large quantities and full length size, trim to uniform length, uniform primer pockets, deburr flash holes, and sort into groups by weight within 1 1/2%. Then I measure for variation in neck wall thickness with a ball tube micrometer and cull brass that is not reasonably uniform. If you don't have a ball tube micrometer, you can mic the diameter of the pressure ring for variances. If there is variance there, it will generally be consistent all the way up through the neck.