Nice short rifle, like ss/walnut and like FL stocks.
Think 2750-2800 with 139-145 class. Do all you need as far as you can hold a steady vitals hold. Powders....I would suspect it would respond similar to a 7/08, 4064, Varget, RL17/19, 4350s. 4320 may also be a good one.
Alot of 'Rigby' owners here can chime in, it will perhaps optimize with a powder a tad different in burn rate than the SA 7/08 round. Use the same powders as in a longer tubed rifle for your carbine IIRC for top speeds.
