H-4831. The last .300 Win Mag that I had started out @ 1/2 moa with a pulled 200 gr full patch, 73 gr H-4831, Rem 9 1/2 M primer. (approach with caution, that was a hot load), but it would belly shoot 10's & X's at 600yds whenever I could. I never found any powder it liked better.
Approach the old powder you were talking about with caution. H-4831 is very linear, but will start to get unpredictable with age (and poor storage).
Lots of good posts on this thread, Tom
Texas State Rifle Association Life Member
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A big fast bullet will beat a little fast bullet every time