Would I be correct in assuming you mostly run across sharpies?
No answer from the OP, but in BC I'd expect they're either Spruce Grouse or Blue Grouse (unless the hunting zone is in the south, where they could also be ruffed grouse).
My experiences with Blues and Spruce grouse are that they aren't generally accustomed to humans. As a result, their survival strategies are usually to sit still on the ground, or to fly to a nearly perch in a tree. In both situations, you're talking about shooting at stationary birds. For this reason, I'd recommend the lightest available loads with small shot, M/F chokes.
- Light loads because lots of pellets aren't needed and heavy loads are just heavier to carry and produce more recoil for no incremental benefit.
- 7 1/2 or smaller shot because it's adequate for a head shot and offers more dense patterns if a wing shot is presented.
- M/F chokes so you can fire the full choked barrel at the head of a stationary grouse and take it cleanly, without damage to the body. This leaves you with the modified barrel loaded in case you miss and the bird takes to the air (Note: Double triggers required to take full advantage of this approach).
When hunting ruffed grouse, my preferences change according to the time of year and the environmental conditions:
Early season ruffies - I use 20 ga., 7/8 ounce of 7 1/2-shot in the open-choked barrel, 6-shot in the tighter choked barrel. Chokes are more open (say M/IC) due to closer shots dictated by thick cover.
Mid-season ruffies - Frost has opened up much of the cover and, in the zone where we hunt, the birds will flush at the least provocation. I move up to 1.0 ounce of 16 ga. through M/F chokes. This offers better patterns at the 15 to 40 yard range of most of the wing shots.
Late season ruffies - By now, I'm usually carrying a 12 ga. with 6-shot in both barrels, choked M/F (unless we're hunting a sector in our zone that offers mixed ruffed/sharptail, in which case I'll have 5 or 4 shot in the full choked barrel).