I know this was an old post but, perhaps this will help someone later. To cure the problem, have someone to polish the feed ramp. Check the angle on and polish the bottom and inside of the extractor. Check and see if the chamber has been properly throated and polished. And if so make sure that the edge in side the chamber is broke and polished. Lastly and this is rarely the problem but, it can be. Check the smoothness of the bolt face. You may have a small burr (especially around the firing pin hole) If you are shooting ANY factory load and your having problems with one and not the other, these things named above should cure that problem.