If I was starting from scratch I would look to R26 and R23 unless I had already stocked up on R22. I am going to try these and R16 next time I load 300s.
Here is the best current data https://www.speer-ammo.com/en/reloading/rifle and also the Alliant site has some loads for these powders.

R23 loads close to R22 and has really good temperature stability plus de-coppering agents. R26 usually gets top velocities with bullets heavier than 150 grains. If the R26 loads don't prove accurate try a hotter primer or just start out with magnum primers.

H7828 is good as well as Ramshot Magnum. I find the 300 easy to load for with anything slower than the 4350s.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli