Winchester has a new powder out called StaBall 6.5 that is supposed to be, as the name implies, a temp stable ball powder, and per Winchester's load data is producing some pretty healthy velocities in cases the size of 22-250, 243, 22/6/6.5 Creedmoor. It could be worth looking at.
I know RL16 is working well in the 22-250 with heavies also.