I have a smoothback magazine i just picked up from SGammo that is giving me some fits. I'm running my Just bought wasr 10. Now i know ones first inclination would be its the gun. But it runs fine with both my other chinese mags, tapco, romanian, and bakelite. When i load to 30 rounds my top round on the left hand side will hit the bullet guide square center. And then for the next 4 or 5 after that if its feeding of the left its nose diving. Not under the bullet guide or below right in the damn middle.  All i can think of is that its a spring issue. Any ideas? i can post a picture if need be.

To decide if it is a spring issue you could try swapping out the spring from another mag.