Center are good, stay away from the Mil mags from Adventure or Sanchez, they need mods. The OLD colt mags from the military that wear down and show a gold colored patina are the ones you REALLY want. I've been snapping up every one I can find for twenty years and they all function PERFECTLY!!!!!
I never heard anything bad about AdventureLine. I know the Sanchez were better with the green follower compared to the black one. If I remember, the AdventureLine was the predecessor to Center Industries.
There used to be a guy on AR15.com, Troy, who had a great deal of knowledge on AR15 mags. He said that many of the USGI mag contracts were set-aside type businesses, and that the unique equipment used in making the mags was passed around to each contractor. Don't know if that is true, though.
Could you tell more about the AdvetureLine mag troubles. Thanks!
sharky8js, you found some great mags.