I don't think the 308 barrel will be all that skinny to have a problem with a muzzle device, but ya never know . Some one here must have one of those barrels & can say .
The light weight BCG set ups, can, have problems with bolt bounce, if not tuned properly ( Heavy Buffer/spring & or an adj. gas block)
If there is one place not to lose weight IMO is the BCG. I like the weight for proper inertia for feeding . Buffer & spring can always be set up for recoil buffering , not to mention lock time .
Competition guns of course are different , I can understand chopping weight off of them any where you can . That's whats good about the AR platform, many ways to tune it .