You don't mention what bullet weights you're interested in reloading for but either 4831 powder is a little on the slow side for the 300WSM. It will work well, but a slightly faster powder, like 4350, H414, or W760 will not require a compressed load to get the best performance. Of these, I would lean most toward W760.
Pay heed to the last two posts. H4350 is an excellent match for the WSM and the temp variation is quite noteworthy as well. You may find more speed with the other powders, but you won't find is the zero "wandering" with the ambient temperature.
Maybe the current run of IMR-4350 is better, but I have found it to be quite sensitive to temperature changes. Actually, this was documented in studies done by the North American Hunting magazine in some reloading articles they did back in the early '90s. I found IMR-4350 to suffer an average drop of ~180fps when going from an ambient temperature of 75 degrees down to 25 degrees. (This from sighting in my gun in CA and hunting in WI.)
In addition to the velocity drop, the inexpensive stock on my Model 70 Ranger contracted, resulting in my POI going from 2" high to 8" low. Had I simply sighted in upon my arrival this would have not have been too problematic, but WI law forbids shooting the day before season opener. In consecutive seasons, I wounded a deer that had to be tracked a long distance before being finished off, then missed a very nice buck...that was when I got smart and checked my zero. I showed up the following year with a synthetic stock and 270 loads with H-4831, instead of IMR-4350. The H-4350 might be just fine...I haven't tried it.
Went to the range yesterday 5-16-2010 & shot this 4 shot group with my Weatherby Vanguard in 300 WSM caliber. The powder was Viht N550 60 gr behind a 180 gr JSP bullet. The spread was .80 in. See the photo attached. I'm going to try & get this in a little tighter by loading a little less powder. We'll see. I was not able to check the velocity as my chrono took a dump on me. The second photo was a little hotter load of Viht N550 and 61 gr. This was a maximum load as stated in the Vihtavouri Loading Manual.
A forum community dedicated to Sport shooters, owners and enthusiasts. Come join the discussion about optics, hand casting bullets, hunting, gunsmithing, styles, reviews, accessories, classifieds, and more!