Op, if you haven't got a barrel yet and your interest is high power, I'd look at Kreiger. They have drop in AR10 barrels listed on their web site and they're a top tier match barrel maker. Using a rifle length gas system, you shouldn't need an adjustable gas block, this is how Mr. Stoner designed it. If you go mid length or change to 6.5 mm or .243 without moving the gas port then you need some adjustablility. Make sure you get a 10 twist as you're going to want to shoot 175's or heavier. Noveski is very popular with the tactical crowd and they make good stuff, but for what you want I'd go with a custom barrel. Thats Kreiger, Rock, Obermyer, Lilja, etc. Good luck & have fun with your build.