My main backpack rifle is a Rem SS Mtn rifle in 30-06 that weighs 6lb. 4 oz. empty w/out scope. Never weighed it full up. I'd prefer lighter.
Years ago I designed and never built my concept of a back pack rifle: Short action for weight saving, 7mm to .30 cal (probably would go .308 to bore out the barrel for less weight and larger bullets with more oomph.) Bolt action bullpup, with an overall length that would go inside my backpack.
That rifle would be small and compact to carry and slow to cyle, essentially a fast reloading single shot. Short, light, handy.
While it is true that heavy rifles are easier to aim steady, I'll opt for light carry and try for close shots or a natural rest, as I do already.
Of course, last weekend I had to stand tall and shoot at a small piece of a buck offhand at 170 yards as my only option with no rest possible.
Tight sling and got the job done.
