Djandj,
You did exactlty what I didi the first time around. The spring OD was around .78" Seemed to work fine. Then I started getting mag jams. The coils of the two springs were jamming. I've been improving the design since.
I just changged the spring wire to .055 from .051 greased the springs and oiled the mag. Did a little polishing and now am getting 25 rds reliably.
Joe
i