I am gathering parts for a .338 build. I had a .338 RUM in mind, however I have started wondering how much benefit there may be to building an Edge instead. Sorry for my lack of knowledge on the subject, but the Edge is a .338-.300 RUM is it not? What advantage in velocity will I see with it and how difficult is the brass to form? Is it just a kneck-up on the .300 RUM? Is the Edge a propriatary cartridge where I have to get some one in particular to chamber my barrel blank? I was considering a 10 twist, would this still be correct??? Thanks!