They seem to stick in the magwell. They are really tight. Aluminum mags work fine. This seems true on several lowers. What's up here please?

Damn man... don't you know that you should always pull out?  

On a more serious note though, sometimes it just happens.  Usually the lower is the culprit; I've had the issue on some andersons.  Really no good solution except to use thinner mags.  IRRC USGI mags are usually the thinnest, Hexmags are usually pretty good, then Magpul M3, then their older mags.  Someone correct me if I'm wrong.

If your using them in only one rifle you could always give them a touch on sandpapering.

"Well loved" PMAGs that have been loaded many times (or for long periods) can bulge out slightly and stick.