When I ordered my first 1911 from Dawson's, I ordered extra mags, and ACT mags showed up. They work excellent in the STI and my Caspian and Para. IIRC thery were around $12 a piece with the pistol purchase.
At a fun show I picked up a few used CMC Power mags for $30 total. Cleaned them out and they have been flawless in all 3 makes.
Found some Wilson Combat mags at another fun show for a rock bottom price and did the same thing: cleaned em out, they work great.
Reliability in these 1911 mags seems to follow the same/similar laws of change: if you take them apart to "upgrade" springs and followers w/o knowing what you are doing, failure is more likely when going to shoot. If you go to shoot and they fail before fiddling with them, you got nothing to lose in researching here, in where to get different springs or followers. Capiche?