I must qualify that I have shot little H1000. Many say it works well in the .280. R-22 seems to be the optimal powder in the 06 family of cases, atlest with those between 6.5 and .308. The velocity gain over H4831 will be nominal in a 22" bbl most likely. But you may reduce pressures some running the same speeds. JME, YMMV. H1000 OTH may not reach its full potential in the .280 case..IOW you may run out of room on the case before you reach acceptable velocity. If so it likely wont burn too efficiently. Again, its something to play with. If you have another big mag...go ahead and buy some H1000, but I wouldn't if the .280 were my sole purpose. R-22 will give you max safe attainable velocity almost for sure, but whether your gun will like it accuracy wise is another story.
And you didn't ask but I'll offer...IMO the .280 does its best work with 140s. Most any brand of bullet will work on deer and antelope, and well constructed 140 bullets are reputed to be adequate on elk sized game. All running 3000-3150 depending on load and bbl length...there's little more you could ask of a .280. Again, JMO, YMMV. You could do a lot worse than a 160 at 2800fps! A LOT worse! I just like to save 160s for my 7mmRM.
Good Luck!
