As stated above, start with a thorough cleaning. While it is apart look for the extractor and ejector to be in good working condition and then look for any other signs of wear or cracking. Ensure it goes together correctly with a light coating of oil on the working surfaces. Once that is done, use factory ammo, preferably round nose ball to ensure correct functioning. The more magazines you have to try, the better, make sure it isn't one with deformed lips that is giving you the problem. The purpose is not to find what works but to identify the problem and then fix it. Good Luck.