In some parts of the country ruffed grouse haven't seen many people and when flushed will fly to a branch (Nova Scocia l970's) weren't hunted much, went there for woodcock only in the early parts of October. Here in eastern Pa. they when you do hear/see them they are gone.
So shooting them on the ground back then in Novia Scocia wouldn't be hard, shooting them here on the ground in Pa. would be harder than shooting them in the air. So shot that small, why not, I have shot many pen raised pheasant and chucker with #8 and #9 over dogs using a 28 ga. 3/4 oz.
I'm not an experienced grouse hunter, too many hours and hardly any birds here.

David