I'm considering buying a Winchester Model 70 in .300 WSM. I have 500 Sierra GameKing 165's and 2000 168 MatchKings, so I'd want loads for those bullets. Any suggestions are welcomed.
I would try Varget. I have had great luckl in several calibers including 300 SAUM. Its similar but different. MagPro also has some high velocity loads for the WSM. IMR 4350 is another good powder; the accuracy load listed in the Nosler book for 165 gr Part/BT grouped very well in a Browning Titanium 300 WSM, 8 shots in one hole at 100 yds and he said he got 1.5 MOA at 500 m.
I'm shooting 180 Nosler Partition in a 300 WSM Sako Finnlight, about 3000 fps and it REALLY hurts. The gun is right now at the smith being fit with a brake. I used the load right out of the Hornady load manual, IMR 4350 and had great accuracy (as best I could tell, gripping the gun with all my might - sub moa for sure). Will report later after brake test.