I got you covered on both sides with a 270 wsm and a 300 wsm. My best loadings for the 270 have been with rl20 and rl19 for my 300. If I remember right Magpro is a compressed load. You may want to check www.shortmags.org they have some good load info there. The short mags site its self has merged with classic cartridge.com and big game central.com on the netrifles home. You should be able to get there through any of those.