I have 6 Luger mags: A WW I era Erfurt, three Tri-Ks with FXO springs, an older MecGar, and a brand new MecGar.
The brand new MecGar is the only mag that has *never* caused me a problem, although the older MecGar has been pretty good, as have the three Tri-Ks. The old Erfurt has caused me all sorts of headaches - despite 2 trips to G.T. Sometimes it stovepipes like crazy and/or won't lock back on last round. Other times, its flawless. I just happened to use it just today at the range, and didn't have any problems. In fact, I didn't have any problems with *any* of my mags today. Musta been the cheap Tula ammo...