Gentlemen, thank you very much for the replies. A few points. First I didn't even know the barrel came in 1:18 twist.
Second I use range brass. I'd love to use only Starline brass but you know how that goes. The same for Hornady XTPs and HAPs.
I have two uppers so I'll try the barrel in each. I will continue to plod along and see what I can do.