I've often wondered why some friends I hunt with get a lot more tired than me and don't want to go up that next drainage 10 days in despite us being similar age and similar fitness level. Couple of years ago we traded packs after talking about the money spent on all the light weight stuff, and I completely understood. I didn't want to carry his pack and rifle up the next drainage either. Every pound matters a LOT, and IMO is fundamental to endurance, which is 90% of success. Does it matter on day 1 or 2? Not really. On day 10-15, it's about all you care about.I'd carry a reliable 15 lb gun anytime in the mountains. My current rifle is right at 12lbs all in. I have not had any issue in the mountains with it. But I like reliable guns that i can bang up and not worry about. Everybody has a preference i guess.
I don't care about the weight of the rifle I take moose hunting. But Moose hunting is not mountain hunting.