I just started reloading the .300 WSM also. I am loading Win brass CCI 250 primers IMR 4350 powder and Sierra 165 SBT. Sierra says starting load is 58 grains of 4350, max is 66gr. chrony 2950-3150. I got .6" group of 6 rds at 100 with the 65 gr load and .5" with the 60 gr load. This was out of a Savage Mod 11
Havent loaded any other brand of bullets yet. let me know if you find a better one!