Well, it looks like H1000 is going to be the powder for now. I tried Retumbo up to 68 gr with 150 vld and 215M and had one five shot group at about .6 at 67.4gr at 2960 fps, anything higher was over 1 moa at 200 yards.
Today with H1000 from 66.0 to 67.0 gr grouped just over .5 moa at 200 yards at 2960 to 3020 fps. That's a wide window for an accuracy node. ( my 270 AI was laughing 150s at about 3150 +).
I'm sure that once my brass is fully formed I can reach a higher velocity node and I will continue load development after my hunting trip. I only have one or two more range trips to narrow the powder charge and verification. But I definitely want to revisit Retumbo and try RL 26.