In order of most grouse killed (by me):
-.22 lr
-.410 pump
-.30-30 win (head shots while deer hunting)
-12 pump
And I've managed to loose 4 arrows trying with my bow.
Very similar...... Mine would be
.22 lr ....... also have taken most of my ptarmigan with a .22.
410 pump and single shot
.22 mag pistol with birdshot. I usually pack that with me when rifle hunting, just for grouse I jump.
12 gauge and 20 gauge before I decided they were both too much for grouse
30-06 those times when I'm deer hunting and forgot my .22 mag pistol.
sticks...... I've actually taken two grouse with a thrown stick. Knocked them out of trees and wrung their necks.
Never gotten one with a bow, but have tried.