I think it would depend on bullet weight. Varget is pretty fast for heavier bullets in the Roberts.

Here's a link to work I did with that round. H100V was the best performer with 100 gr. TTSX, H-4350 with 115 gr. NBT's.

http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/10163944/6

DF