One of my AR's has a 1:9 twist bbl. It seems not to like any bullet (jacketed lead) over 60gr. It will shoot the 60gr NosPart's great but not anything heavier.
The Barnes 62gr TSX does not shoot good (4MOA) at all. Have not tried anything heavier. The bbl is marked "1:9" and have confirmed it with a cleaning rod. I have cleaned the bbl very well using JB Cleaner and checked it with a bore scope.
The gun is a keeper and the 60gr NosPart is great for these NW Fla. deer. I can live with that. --- SAWMAN