NYresq

compared to a 223, everything is larger and therefore heavier. The BCG, the barrel, the buffer tube, the buffer itself, the hand guard and any muzzle device you add will be heavier then the same component in 223 size. I think the trigger group is about the only part that will be the same (depending on brand, some use heavier hammers for 308). Even the grip may require a spacer block to fit some receivers properly. if you want to keep the weight down, forget the UBR stock. I had one for about an hour before I sold it. It uses a proprietary buffer tube and it weighs a ton compared to something like a CTR stock. Stay basic and simple and you should be able to get close to 8lbs without optics.

And the ADM wont chewmup your rails if you take it off and on with any frequency. The Larue cam has a tendancy to wear away at the rail as it rides under and locks up. The ADM only squeezes between the side plates. After seeing the damage done to a rail with a couple different larue accessory mounts, I sold them and swapped them all to ADM QR mounts.