When reviewing the posted "favorite loads" of 300 Ultra Mag shooters I noticed that many of them are shooting at velocities that are easily obtainable with a 300 Wby. You would assume that people buy rifles chambered for RUM cartridges so that they can shoot at RUM obtainable velocities. However many seem content with Wby performance. Hmmmmm
My load for the 210 VLD loaded .015"-.020" off the rifling is 101.1 US869 in a Federal case with a GM215M primer. It usually holds less than .5moa @ 300yds and flys over my Oehler at just under 3,200 ft/sec. It also produces less pressure than any other powder that I've tried.
Not many shooters seem to be using the (Hodgdon) US869 but it is certainly worth a try.