I have a bunch of MecGar 9mm 1911 mags. A couple in 45 too. I got the 45's in trades and they work, so I kept them.
I have a 9mm Colt Commander and recently picked up a Tisas GM in 9mm. I use the same mags in both guns. The Colt, for the most part, doesn't have any problem with them. The Tisas on the other hand, doesn't seem to like them as much, and has some trouble with them on loading, especially from the slide stop. They usually work better if you slingshot the slide. Once the gun is loaded and running, they usually work fine.
First instinct is to blame the mags, but I dont think that's the case here. The Colt has a standard 1911 barrel, the Tisas has one of the "ramped barrels, and I think that's where the problem lies.
I watched the rounds go into the chamber on the Colt, and they hit that short ramp and pop right in. They really dont have any choice either.
I watched them on the Tisas, and what happens on occasion is, the nose of the bullet hits the ramp, and then deflects downward, on the ramp, and stops, and ties things up.
With the Colt, there is no "down" for the round to go.
So, I have to figure out whats up with the Tisas, and try and/or find 9mm mags that wont allow them to nose dive into the ramp.
Ahhh, the endless and ongoing joys of fooling with 1911's!