If you unload, remove the slide, and insert the mag slowly looking down from the top you can see where they could be binding. Often one brand of mag is a couple thousandths thicker so it could be the side of the mag catch, grip screws rubbing, etc. Just removing the mag catch will sometime quickly isolate it. On one or two guns, I've needed to relieve one side of the mag catch with a couple strokes of a file. One of my Baers is was just a little narrow in one spot so it needed a couple strokes inside the frame to work with my mags. Sometimes its a 2 minute fix.