12-13-2011, 09:34 PM
Does this happen with every mag you try? While shooting my Grendel carbine a couple weeks ago, I had terrible failures to feed from one side of a mag. These failures to chamber resulted in huge dents in the shoulder of the case where the shoulder came into contact with the lugs of the extension. I removed the offending mag and immediately noticed that one of the feed lips was not like the other. After comparing the feed lips to another mag to make sure I was bending the correct lip, a little tweaking with a pair of pliers remedied the failures. Doesn't really sound like this is the issue in your case, but it's an easy and cheap thing to check.