Most mini mags out there do suck.
The 30 rd ProMag clips I have now are good, but only because I dremeled them. They fit fine, but the upper lips were so thick that they blocked the bolt from even going forward. I had to sit there and shave them down to kind of a pointed edge just to get them to work, and if I had shaved them down much more, they wouldn't hold the round in place.
You'd think that these manufacturers would at least stick them in a rifle and cycle a few rounds through before attempting to sell them to the public. I guess a little QC is too much to ask for these days.