I've got a 16 inch barrel with 1/11 twist. It was made by Stag Arms. If I do my part it will shoot MOA. I think I've had it about ten years now.

If I were to do it again, I'd go with a heavy barrel and a mid length gas system. Make sure it has an M-4 barrel extension. Maybe 18 inches. I don't think those specs existed when I built it.