My wife and I have hunted ruffed, spruce, and blue grouse several times in the NW corner of Montana [around Libby].
Always in conjunction with a black bear hunt. Several times we have gone up a week early JUST to hunt grouse.
We have used 20 and 12 ga shotguns as well as 22 pistols, reduced loads in a 308 [did not work as they were not reduced enough

], and Speer shot shells in our 44 pistols and a 45 ACP.
We love to eat grouse and I freely admit that we will "skillet" shoot them when ever possible. I like to eat grouse so much I would shoot one off the shoulder of the Game Warden.

Usually you can get pretty close to these mountain grouse and light loads of #8's and 7 1/2's work fine.
We have taken many a grouse [several flying for you purists] with an 18 1/2 " 20 ga double.
We cook them just like fried chicken.