Dunno if Wyoming allows shooting grouse with a rifle, but Montana allows rifles of any chambering for "mountain grouse," which means ruffed, spruce and blue grouse (these days sometimes called "dusky"). Have shot the heads off all three with big game rifles chambered for rounds from the .257 Weatherby to the .338 Federal and .338 Winchester Magnum. (Also have killed quite a few with my Colt Frontier Scout .22....)
