20 gauge full choke here. #6 for me, longer shot, pellets usually pass through, and they can knock down the occasional blue that we see. 5’s are handy if you are also taking rabbits. 7 1/2’s tend to stay lodged in the breast, and there tend to be more of them than if you use 6’s. Love grouse hunting, and is my favourite game meat to cook with.
Trouble is easy to find and hard to get rid of.
-Solomon