Used 10.5 in ballistic advantage stainless steel barrel and gas tube/block. The block is missing the set screws. 1-7 twist 5r threaded 5/8-24. Shot less than 150 rounds out of it. Could use a good sand blasting from where it's been in the parts drawer. Shot several 3 shot groups between 1-and 1.5 in suppressed with the hornady subsonic ammo. 140 shipped