I already have a good load using Varget. However, if I couldn't leave well enough alone, what powders are giving higher velocities out of the shorter barrels?
RL 17 definately interests me. I have RL 19 but it might be a little too slow. I have zero experience with IMR 4064 or W 760. I guess it will depend on what's available.
Those 3 suggested, RL-17, IMR4064 and Winchester 760 are all fine powders for your application. I would lean to RL-17. All seem to be on the shelves at the moment.