Well, if we're in the Arctic. Then I guess a Lee Enfield, since that's what the Canadian Rangers use to patrol the rather cold parts of Canada. A weapon like the M4 is going to freeze up pretty quickly in the temperatures that you can expect in the Arctic. But that would be a little hard to use, honestly, I'm not sure on what to suggest, maybe the M417, which is probably no better. Since pretty much any weapon would freeze up in minus twenties.