The Armalite AR-10 is a sweet semi-auto .308. But the model that's even sweeter is the AR-10T (target) which is similar in configuration to the Colts CAR-15 H-Bar Elite, except in .308. This version has the slab top receiver to except your favorite sighting optics and has a heavy s.s. 24" barrel. It comes with 2-10 rd. mags, but you can get 20 rd mags from Armalite for it at about $60 each.
The Armalite AR-10 goes for about $1,200.00 and the AR-10T goes for around $1,400.