The V2.0 prototypes came in. They need a few more tweaks, but otherwise the mags lock up snug and the rounds feed well & eject strong.
As I expected, the Uzi Pro mag is much better. When a surplus Uzi mag is set at the corrrct hight to feed the rounds, the follower is so high when empty, the bolt gets hung up on it. Also the feed angle is such that the rounds just don't feed very well.
I hope to test fire it this week. Fingers crossed.
Oh, and I bought a 3D Printer.