I do appreciate the info so far.

I experienced lots of base over bolt failures when building this thing. There were failures to extract and failures to feed.
After installing and head spacing the new Criterion barrel, dropping in a new gas piston with nut, welding up and fitting the guides on the slide, and replacing all the springs with Fulton Armory stuff the failures went away.
I also cleaned up the receiver, trigger group, and bolt bits.
In short, it's a fresh build that functioned beautifully with the remaining IJ parts as well as with GI parts from my friend's Inland. Even the head space was on with his bolt.
The little guy has been 99% reliable since the rebuild. A couple failures have happened but they were a result of my reload development.

The failures I had during the match had a live round poking it's head into the chamber with the bolt trying to strip a round out of the magazine.
It was a double feed in my book. I don't know what the technical term might be.
The empties were going away nicely and function felt normal until the jam would hit.

The only thing I did differently was load the magazines the night before the match. The idea was to minimize the amount of stuff I had to carry. If I took two ammo boxes I would have needed to use the much larger case or leave the gun tools and cleaning kit at home.

Is it possible that the lips spread out on the magazine and rounds were popping out under recoil? The loads I was using are right down the middle of the charts with 100 gr bullets at 1950 fps. It was the most reliable load during my testing.