Just an opinion but often when folks think mountain rifle, they think solely weight. Lug an ungainly/poorly balanced rifle around the steeps for a week and you'll appreciate good carrying characteristics. My favorite mountain rifle to "carry" is a Marlin lever-action 1895. The short barrel, narrow receiver and good balance make it a dream to carry. It's a 7 lb. rifle without a scope but you hardly notice it's in your hand.
Not saying a lever-action is appropriate for an open country situation but the point is that it has characteristics that make it very good to tote. Translate that to a bolt gun and you have a 22" to 24" barrel (so it doesn't dig into the ground on uphill ascents), a not-to-thick stock and a reasonably weighted scope so it's not top/forward heavy. Light weight of course is good too but ultra-light often comes with compromises in performance. Actually, "ultra" anything has a way of generating buyers remorse.
Not saying all mountain hunting rigs should be like that but just noting that 99% of the time, you gun is in your hand so good balance shouldn't be overlooked.
