I know exactly what is wrong with your 60, I've had that happen on four or five new 60's, I'm always one to tear things apart and find out what's wrong myself before going to anyone for help.........that thin wire is supposed to be there under the bolt, just not where it is...there is a groove on the "magazine lip" that the wire is supposed to sit in, and it has been pushed out of it, take the gun apart (easy as pie) and replace the wire where it's supposed to be, you can also scratch the groove a little deeper and sharper so that it locks in better. You might also try bending the wire slightly so that it sits better in the groove, if I recall correctly, one of my 60's wire wasn't bent at all, so it kind of layed acrossed the gap, so it jammed like that a lot.

If that's not it, I don't know what it is.

I'm not certain why the wire is there, thinking back on what it does, I'd guess it's the ejector, but it's hard to believe that they put one in that small/thin.