I have Long action Remington BDL (aluminum black matte finish) with a Remington magnum magazine box and spring and follower and I've tested my 7mm WSM empty brass in it and it loads and LOOKS like it would feed OK, but of course I DON'T HAVE an ACTION! I also have Magpul bottom metal and Magpul magnum magazines that my WSM brass will fit in and SHOULD feed OK. I shortened a Magpul 5 round to 3 rounds and it fits fine and looks factory and is much lower profile if it was in a hunting application. That brass is .550 so I think a 6.5 PRC at .532 on the base and .515 at the shoulder would fit and feed fine, especially in my preference of a CRF long action. I don't know if there is even any short action bottom metal and boxes and followers available anywhere for magnum size cases, Brownell's sure doesn't show any that I can see.