First, 6.8 was designed from the ground up to provide 50% more power than 5.56 and do it from a 14.5" barrel. An NFA legal 16" barrel adds it's incremental power. 6.8 will do the job just fine on deer out to 300m and shoot flatter than .300BO supersonic. It's in the .30-30 class of power and that cartridge pushed the whitetail to the edge of extinction by 1930. If you are hunting broken woodlands then little more than 2X would be needed - I tried the scoped bolt action in the day and I won't go back. Even at 3X close range gives you a field of view that is largely fur, and the recoil plus so much power the bullets pass thru the animal mean it's more than you really need. Bolt guns also force the shooter to remove his eyes from the field of view to reload for a second shot, much less the recoil creating it's separate issues. Keeping your nose to the charging handle and squeezing off another shot comes much more quickly when needed shooting the AR.
A 6.8 built light should scale under 6.5 pounds, the two major items are barrel profile and what free float tube. A completed gun can easily run less than $1,000, which is what I paid for all the parts retail when I built mine four years ago. If anything the real issue is that so many of the parts available come in one color. Black. And that isn't what you want or need. Buying furniture of another color helps, consider that the Army has instructions on how to spray can the gun for concealment purposes and it works. If you still hunt or desire the weapon to remain low visibility when you hunt - don't go black. Avoid it. Mine is Foliage Green, including paint on the forged parts, and it's developing a nice worn patina which actually increases the camo affect as it wears down.
You will like the way the AR lives in the field with that kind of finish, as it gets pushed thru brush or rests on limbs, etc., you don't worry about special decorative finish and can concentrate on the job at hand, not the wear on an "heirloom" rifle. That AR will likely be handed down in better shape than some glossy walnut and blued manual action that rusts under the rings and stock like a 1911 recovered from a trench days after the battle. Carbon steel guns are notorious for it.
Handloading the 6.8 dellvers a lot more performance. Look to the SPC II specifications, read up at 68forums. I've seen posts where some are getting well over 2900 FPS from 90 grain bullets. Actually, quite a bit more, but some would scoff at the numbers. 6.8 isn't about speed, tho. Those bullets carry more weight for a reason - in some cases more than double what 5.56 is loaded, and with that much more mass in hunting rounds there are plenty of results. It's doesn't take a .308 to bring down whitetail - again, the .30-30 and rounds in the same class, like the .30 Remington the 6.8 is based on, nearly drove them to extinction. Most of those were shots under 150 yards, too.
Where I hunt the usual setup in the woods leaves ranges under 80 - and in response to that and to take advantage of an alternate weapons season in MO, I built an AR pistol in 5.56 with 10.5" barrel. Ammo still carries over 1000 foot pounds inside those ranges, but its a much flatter shooter than a .45 with more power downrange than what ACP starts out at the muzzle. The point is that you pick the cartridge and it's power level for the job, not vice versa. That way you hunt with enough gun knowing your limitations, rather than overcompensating for that one situation which rarely takes place just to attempt a shot.
I agree - hunting with a large heavy manual action gun isn't all that, especially in denser woods and where the shots to be had are far under the guns capability. Reading into antelope hunters posts the 11 pound weight is well over their limit for stalking shots even at 300m. A good AR would be far better in the woods - it's the natural successor to the lever gun and certainly doesn't take second place in handling or power.
