So besides being hard to source, the 5rd Ruger x39 factory magazine magazine works well....ok good to know.
I recall back in the day the XCR 10rds x39 mags seemed to work best with only 8rds.
Regarding mag release, any pros/cons of factory release setup vs the mag adapter release system?
The Mini-30 mag is a bit easier to use, but it's not significant.
The XCR mags seem to work best with 8 or less rounds in them. All of mine work well with at least 6 and one is good with 10. It's dependent on the individual fit of the mag in the adapter and how much wobble there is.