.22 mag. for the simple reason that it will deliver more KE than the 17hmr can. I'd go with a 45 gr jhp, as long as it was accurate and you can make the shot. Be prepared to do some tracking, and I hope you have snow because any runners, and you will have runners, won't be leaving enough blood to follow without snow on the ground.
I've got a friend that used to use a 22 mag., and he shared plenty of storys with me, and enough of the storys included lost animals. SO I'll I'm going to say is, good luck!