I have done some testing with different brass cases of different manufacturers, all other components were the same. If you change the case you are going to change the pressures and the harmonics of your rifle with said load. I don't necessarily believe that one brass is that much more accurate than another,but I saw that a couple of different cases would group about the same. The only reason I was checking was to find out if any of them were interchangeable. I has some Lapua that did not group well with the charges used, that does not make that brass inaccurate, it just meant that I would have to change some components.
