Indy,
1) As far as I know it is still a country free enough to allow anybody to load what they want to. But in general somewhat slowwr powders than H4831 will produce good velocities with heavier bullets.
2) In the early 1960's a LOT of data was hotter, mostly because of the relatively primitive pressure-test methods common then. IMR4350 has also changed a little, but the big deal is better presure data.
