Those ACT mags are the crappiest feeling mags I've ever used, plus they have a non removable bumper. I won't use a mag with a bumper.
Yeah, I'm not a big fan of ACT either. I had one downloaded to six rounds at a shooting event this summer, and when I went to speed load the mag during timed competition the base pad popped off and the mag dumped the six rounds all over the ground. I typically run only Wilson Combat mags, but ran the ACT's just because I had them laying around and wanted to see how reliable they'd run. That pretty much answered my question.