Generally when I run into a pressure/velocity "wall" with a powder,and velocities are sub standard, I usually go to a double base powder of slower burning rate. I would try R22, R23, and even R26. I would go double base because they generally have more powder energy than single base and many times produce more velocity.
In this case I would start with R22 (if R19 bombs out) simply because I have BTDT with the cartridge after IMR4831,IMR4350,and RL19 failed to give the best combination of accuracy and velocity.
RL22 proved to be the sweet spot for my rifles in the 280. I know there are other today.
The only cartridge I can recall that did better going the other way was the 30/06....
RL22 bombed out velocity wise; RL19 was better but charges were almost as heavy as RL22.
Next step was back to H4350, which hit the sweet spot in velocity and accuracy and I have not changed from it yet with 165's,which is all I shoot in a 30/06.
