Tim,
My brother has a VEPR .308 with a 20" barrel. He likes Alliant powders and for him we used RL-15. I made him a box of ammo while he was visiting beginning at 42gr. and ending at 45.5 gr. with the same trim, seating, and using federal brass and Remington primers. He has not checked the velocities yet but 44 gr. seems to work well while 45.5 is nearly a compressed load when seated and crimped which improves consistency.
Since I like Hodgdon powders, with a 22" barrel I might try a ladder test with Varget to squeeze every inch out of your barrel. I like the extreme powders due