Range report #2:
I took the gun back to the range after polishing on the chamber some.
I tried a bunch of stuff including going down to 1.76 gr and 1.5 gr of D032 with the 55 gr bullet. Lower power loads seemed like ignition may have been getting less consistent. Accuracy was not so good and I seemed to be getting vertical stringing.
I also tried some loads with 78 gr PC bullets and warmer charges of D032. A 2.76 gr charge (QL: 1138 fps @ 13680 psi) shot better than the low power load and gave me my best 5 shot group of the day. A 3.0 gr charge (QL: 1212 fps @ 16284 psi) shot similar. Both of these extracted easy and are doing some amount of fireforming.
After seeing the vertical stringing and the improvement with the warmer loads, I went back and fire a bunch of rounds with the 55 gr bullet over 1.76 gr of D032, but made a point of tilting the gun up just prior to firing. The groups size improved and the vertical stringing went away.
Right now accuracy is ok but not as good as I want it. I took the gun apart and drilled and tapped for the front sight. I think I will shoot it with open sights and fire form loads for a while. After I get a pile of fire formed brass, I will put the scope back on and try to find a more accurate load. If things do not improve, I may make a chamber reamer and re-cut the chamber.