I am currently loading for three different 300WSM rifles, so I have used so many powder and bullet combination that I don't know where to start.
I will give you just a few that have worked well in one or more of the rifles.
First in my Winchester Model 70 Coyote, the first load that shot great was RL-19( 69-70) grains in Norma cases, WLRM primers,165 Nolser Partitions and 165 Nolser Accubonds. This led me to shot 168 grain Sierra Match bullets with 69 grains of RL-19 which is a very good load for paper targets.
I am loading 168 Barnes TTSX bullets for my Ruger Mark II. My elk load is 64.7 Grains of RL-17, Norma cases, WLRM primers. This load reaches about 3000 ft/sec and is not a max load. Another powder that I have used with the 168 Barnes TSX and TTSX bullets is N550. This is a very good powder for the 300 WSM
. I used 62.5 grains to get 3000 ft/sec. and again this in not a max load.
In the last few months I have been loading Berger bullets for a friends Model 70 Coyote. We have used 190 VLD's 168 VLD's, and we have settled on 185 Match for his gun. Some of these loads have been very accurate. We have used N560, IMR-7828 and N165. My friend just shot a .60 three shot group at 200 yards with the 185 Match, Norma cases, 215 primers, and 69.0 grains of N165.
What I take from all this is that there are a great number of powder that will work well in the 300WSM. First find a bullet that your gun likes and almost any of the medium slow to slow powders will work. I think the heaver bullets like the slower powder and the lighter ones like the medium powder.