I will say back when I chased accuracy, the CLE Krieger barrel I had was the most accurate barrel I’ve seen. But it also had the tightest chamber I’ve seen as well and I had to keep cases separated. Not what I want to deal with on a GP carbine.
The OP may want to consider something from White Oak as well. Their match chambers are a touch looser than CLE, but still tighter than more commercial producers. I prefer CLE's gassing, however, but that's talking heavy barrels.
