Still no good.
Pulled those 40 grain loads and backed a few down to 35 grains.
First I merrily fired-off five PPU factory 140 grain bullets, just to make sure it was good. It was fine - accurate and easy to cycle.
Then I loaded a single 35 grain 2209 / 160 grain Woodleigh PPSN and the bolt jammed rock-solid. Had to go home and open it with a hammer. The primer had popped.
I think I’ll send it to a gunsmith when things open up again.
It’s frustrating.