I had a 26" 6.5x284 CBI LV barrel that really liked 49.5 grains of RL-17 with 140 grain Berger VLDs touching the lands. I sold the CBI barrel which was a little heavy for my intended use. I replaced it with a 22" Savage factory sporter barrel in 6.5x284. This barrel does not perform very well with RL-17. But it is lights out accurate with 50.5 grains of H4831 and 140 grain Berger bullets. W760 at 47.7 grains is my back up powder due to current shortages. H4350 would also be on my short list of powders to start with for a 6.5x284. It has been consistantly more accurate than RL-17 in all the .260 and 6.5x284 barrels for which I have worked up loads.