My experience with the 14 round Mecgars-bought 3 for my CZ75B .40 S&W. When loaded to 14 rounds I had to almost beat them into the mag. well. Dragged/hung really bad. After seating they would not drop out when I hit the mag. release if still loaded to 14 rounds.
Down load to 13 rounds and they would insert/release/drop out just fine.
I removed the +2 bases, put them on some M&P 9MM magazines and put standard bases on those 3 Mecgar magazines for a total of 12 rounds. They work fine that way.
I did replace the mag. springs, too. I noticed they would barely raise the slide stop up when the mag. was empty. The slide stop would just catch the lower edge of the notch in the slide. I put Wolf +10% springs in them and then the slide stop would move all the way to the top of the notch in the slide, like it's supposed to do.
I still by Mecgars. These are the only 3 I've had issues with that were a magazine issue.