I started with Magpro,others said that powder was made for the WSM's . Started with 64grs and got high of 2,918 and a low of 2898 . I stopped at 67.0 grs High of 3,056 ,low 2,990 . All loads shot poorly at 100yds. I know I have a 9"twist bbl. Anyhow I'll be putting the Magpro back on the shelf .
I have read that Magpro is primer sensitive. the favorite is the 215 and 250 the worst, standard large rifle also had problems it was something to do with getting the proper ignition of the powder. the ones that got it to work liked it but took a lot of trial and error