IMR 4064 out of the same jug. This barrel just likes it better than anything else I have tried in it, h4381sc, h380,w760, h4350,h4320,rl19,rl17,rl22.
Before groups fell apart this barrel shot 130 and 140 grain Nosler accubonds. Both would shoot 0.350 groups. The 130 liked 37.0 grains and the 140's 36.0 grains of 4064. When the groups opened up I tried more and less powder, different seating depths--lots of things, different primers. No good. Now the barrel likes ( am going to try again today) 120 grain Barnes TTSX over 37.5 grains of 4064. Seated 0.40 off. Tried 0.50 off and 0.60 off, 40 was the best with 0.30 group at 100 yards. Before this barrel would not group Barnes any better than 0.925. I kept track of all the different things I tried. Barrel also hates BR primers, or at least the CCI's. Likes WLR primers best.