So who else was ringing steel at 200 yards today

[Calculon]

Hard to advise wo seeing and more info but I would try the following:
Disassemble the mag.
Run a stone or Emery cloth or some very fine sand paper on lip edges. Nothing huge, just to remove any burrs or shap edges that cut and drag in the mag.
On the front end also round the edges so sligthly.
For a 10 rd mag you can cut 2 or 3 coils from the spring enough so there is tension but not so much.
If you test the tension with your finger before you start this and after you will feel a lot smoother travel.
Also in the barrel extension / receiver contact point right under the feed ramps make sure it is very smooth. Sometimes this requiers a dremmel and stpne and then polish the ramps. Wash everything well after this and clean flush chamber and bore from any dust and abrassives.
Also try other mags before this but this might help now or in the future.

Thanks Meke. I'll give other mags a try first. I know it's hard to diagnose sight unseen - I didn't want to be "that guy" but I guess I was after all

If I see anything odd I'll post a couple pics.