RE: good starting powder for 7mm Mag
I guess we all know that individual guns will tell you what they like the best, and the only wat you will find out is by trial and error, with a little good judgement and knowledge thrown in too.
My buddy's Sako 7 mag likes 4831 for the 140 gr., and my Ruger 77 likes 4350 with 139 gr. His rifle won't shoot my load well, and mine doesn't like his. Personally, I try to achieve the most accurate load I can with the most velocity. If the accuracy falls off with increased velocity, I try another combination or settle for what shoots best in that particular gun. I'm more of an accuracy nut than speed but achieving both in a safe, repeatable loading is why we handload, and the satisfaction we get from building our own custom-tailored ammo.