H4831 is the gold standard powder for the 6.5-284. Mine loves it, but I really get better velocity with exceptional accuracy using RL23 with 140 gr bullets. Retumbo and RL26 are other good choices.
I know you are trying to stay away from RL22, but I used it with the 140 Ballistic Tips and it's awesome. I developed the load during the winter, so temps were similar to hunting season and I've had no issues