I've hunted with 10+ lb rifles and would do so again if I felt that it would make any difference in my odds of taking a game animal. Where and how you hunt matters too. Some days I may only walk a short distance and sit in one spot all day. On other days I've put in as much as 7-8 miles in steep terrain at altitudes ranging from 9,000-11,000'. More often than not for me hunting involves at least 2-3 miles of walking and almost always in steep country.
For a long time I chased the lightest rigs I could put together and that culminated with my 308 Kimber. With the right scope it is under 6 lbs scoped. It is a joy to carry and has the potential to be as accurate as any rifle I own. But I don't shoot it as well as I do a rifle just a bit heavier.
I've come to the conclusion that something between 7-8 lbs scoped is about perfect for an all around rifle. Not a burden to carry, and enough weight to hold steady for accuracy. 7 1/4- 7 1/2 is perfect for me. Any lighter than 7 lbs and I don't shoot them as accurately.
Once you get near, or over 8 lbs and I find the rifle slung over my shoulder more often than not and I don't shoot anything over about 8 lbs any better. Closer to 7 lbs and it is more likely to be carried in my hands and ready for unexpected shots. That is the real difference to me. Carried slung over a shoulder a 10+ lb rifle isn't that much harder to carry than a 6 lb rifle.
I used to obsess over the lightest scope I could put on a rifle. Scope weight is still a factor, some weigh as little as 8 oz, some over 20 oz. and depending on the intended use it can make a big difference. On a 30-30 I'd much rather see a small 8 oz scope than one weighing 16 oz or more. But on a bolt action rifle I no longer worry about 2-4 oz if I think the heavier scope is better.
My ideal all around rifle. Winchester EW 308, McMillan Edge stock. It is a little under 7 1/2 lbs. This was taken at about 10,000' in Colorado. I put in about 5-6 miles before getting back to the truck that day. None on level ground.
I was asking because i want a browning bar mk2 safari, which is an 8 lb gun.
I think there are a lot better options than the BAR, and excessive weight is just part of it. While they are well made guns a bolt gun costing significantly less is going to be more accurate, have a better trigger, be more reliable as well as lighter in weight. In order to function the ammo used in semi-autos has to fall within a fairly narrow pressure range. Too much, or too little and they don't work. Same as to cartridge specs. You're going to be limited to factory ammo, or very carefully put together handloads that meet factory specs. With a bolt gun you have a far wider range of power levels that will reliably function.
And speed or repeat shots just isn't really a factor. Yes, you can dump the rounds out of a semi faster than with a bolt gun, but if the goal is to actually hit a target there is very little, if any, difference in rate of fire.