I've been trying to get enough 300 win mag brass to replace my older 5× shot brass in a few more firings. So far I've acquired 3 lot numbers. I weighed 20 random cases from each lot#. They all were within 4 grains of each other Which is 1.6% of the heaviest cace weighed. The neck thickness average is the same for all lot#s. (I'm not even going to go into the neck thickness variance). I would LOVE to mix all lots but everything I've ever read or told is to keep lots separate. I recently called Winchester (Olin) about this and was told all my lot#s were the same.1hc31 1hc11 1hc41. I ask him if these #s indicated different machines or sheets or days made he told me it was "proprietary"! (Which pissed me off) and that every piece of brass made since 1970 something has been made from the same recipe of brass which is hard to believe. Should I combine or just be happy I finally have enough to make a useable amount and shut up and start shooting.