I recently bought a couple of gen-2 Tapcos with the little steel clip. I haven't taken them to the range yet, but I have played with them some in my 581. They are harder to insert than steel mags, seem to be just a little too big. Not sure if it's front to back or side to side, but seems front to back. But once inserted, the follower doesn't bind.
Also while checking the follower, I managed to have the bolt fly forward and smash my index finger tip and punched a neat little firing-pin hole in the side. Kind of like "Garand Thumb". That's not the mags fault though, that was my stupidity.
I sure hope I don't do that again...
Anyway, the Tapco mags seem usable but I don't know for sure yet. I won't be buying any more unless they loosen up with a little use. I did order a bunch of steel mags from CDNN last weekend. I bought one of their 20-round JB1420 mags a few months ago and it has worked flawlessly, so I ordered 2 more just like it and three JB1430's. $13 and $15, respectively.