Bronco, I don't load the 7mmWby, but my advice would be to talk to the folks at Berger, and check out the Nosler data on their Web site. In my Weatherbys, I've had the best results from IMR7828, H1000, and RL22. Your rifle may like something different.
I'd also say, what works for long range paper targets may not be the best bullet for long range animal targets, so keep in mind your intended use.
For reference, the longest reliable practice option I have has been 500yds, for a long time, so I won't shoot game out beyond that, since I haven't practiced further. I have a longer practice option now, but haven't invested the time and effort to declare proficiency (and may never be comfortable doing so). The good news is, I've never had to shoot game even at 500yds, so it isn't hurting my chances. I can usually get closer than 200, but so far always closer than 450.