The automag II is reliable but picky on ammo as it had to do with the pressure curve. Used to have one....one of several handguns I miss.
Just a bit of info here.
The Automag II was never "picky on ammo", per se. It was just designed around the Winchester .22 WMR cartridge at the time. Not all other manufacturers of .22 WMR (at that time, anyway) had the performance characteristics of the Winchester .22 WMR. This was due to the powder that Winchester used, if I recall correctly.
Also, if I recall correctly, the owner's manual specified using Winchester .22 WMR for this reason. I don't have mine in front of me right now, though, to cite the chapter and verse.
So it wasn't "picky" in the sense of it simply being designed to use .22 WMR...it was designed around a specific brand of .22 WMR at the time. If you used what it was designed for, you wouldn't have any problems.
That said, I tried three different brands of .22 WMR at the time: Winchester, Federal, and CCI. Winchester functioned flawlessly, I don't recall any problems with the Federal, and CCI would produce some failures to cycle properly.
I haven't done any research recently, but it seems to me that I recall reading a few years back that CCI, and other manufacturers, have since changed the powder they use in their ammunition and that it will work fine in the Automag II. I can't cite the references, so take that for what it's worth to you.
Bottom line: The Automag II was specifically designed around the Winchester .22 WMR. Use that and you shouldn't have any problems. Any other manufacturer, you should function test and see if it works or not.