I have a Tikka T3 in 300 WSM, and I tried 9 different powders and shot 350 rounds working up a load. I use the Hornady 165 grain Interbond because it was the most accurate and stayed together after being shot into wet newspaper.
The most consistent, most accurate, least temperature sensitive, and least fouling of all the powders was Reloder 19. Groups were the most accurate when the ambient temperature was 70 or below; groups opened up slightly when the temp was 90-100 degrees.
I used 4 different primers and Winchester large rifle magnum primers worked the best.
My fired brass measures .0008 smaller at the case head than fired factory ammo.
Using my chrony, my loads are exiting the 24 inch barrel at 3114 fps.
I am not listing the amount of powder I use because it will be different for your rifle. My buddy's A-bolt uses 3.3 grs. more in his rifle and his case heads are still smaller than fired factory ammo. Chamber sizes are just a little different for each gun.
You will love the 300 WSM, Have fun with it.