Re: CCI Primers???
My 300 WM and 338 WM both seem to like the CCIs and Fed GM215M about equally (and a good thing, too :-) with the scarcity of Fed primers), and group about the same. I've also used the Winchester mag primer, but neither rifle groups as well with those (and they seem to bump pressures more). Only way to tell for sure is to shoot them, though...