Re: primers for the 300wsm??
I originaly started with Fed 215 and Rem 9 1/2M but went to standard rifle primers looking for smaller groups and lower ES. In a side by side test using my most accurate load and CCI 200, Win LR, Rem 9 1/2, and Fed 210, the CCI's were the clear winner. The others were fine for hunting and I would'nt hesitate to use them now but there was a noticable difference in group size and ES with the CCI's. I also noted a difference in average velocity between the four brands. That was with H4350, 165 and 180 Sierra GK, 180 Partitions, and 180 TSX. Your loads may show a preference for one of the others depending on bullet, powder type and charge weight, etc, so you'll need to try them and see.
Hope this helps