Bear Creek sent a new barrel about 10 days ago, and things slowed down enough over this weekend to reassemble and test. First, the barrel was a smaller diameter (0.75) at the gas port than the original barrel, so I used a new adjustable gas block for the reassembly. All other parts besides the barrel and gas block were the same. With the port wide open, and with stock buffer spring and buffer, the bolt was riding over the ammo again. But I closed down the gas port 50%, and actually managed to get a full 3 round lancer mag cycled through without a hitch.
As I ran more rounds through the gun to get the scope adjusted for 50 yds, some failures to feed started cropping up again (always the 2nd round). But overall, I think I have a potentially functional gun. Now I just need to work out the balance between buffer spring, buffer weight, gas port adjustment, and mag spring strength. Probably not taking this one to shoot pigs next weekend, but getting closer! Gonna need more ammo
But until it functions properly with Winchester factory ammo, I'm not going to introduce handloads.