I have gotten quite a few with both a .22 rim and .22 mag. In most cases I shoot for the base of the neck rather than a headshot. This is because when a grouse is about to fly its head bobs around quite a bit but the base of the neck (where it attatches to the body) is stationary. If shot here really doesn't matter if it is a solid or a hollow point.
Then your username should be neckshot!

I agree with you. The base of the neck is a great place to shoot them. I've killed hundreds with rimfires, and personally switched to the .17HMR because of the "mini" v-max explosive bullets they offer. I've had a couple flyoff and even roll off a steep hill and get his wings under him while using a .22lr. With the v-max bullets, if you hit any part of the neck of head, they aren't going to survive. I've recently acquired a 17 mach2 from a member on here, and am really looking forward to see how it does. I'm hoping the trajectory will be a little flatter from 10-50 yds, whereas theres 3" of difference with the HMR.