I was at the range this weekend shooting one of my AR's when it suddenly started double firing. Initially, I thought it was just me but a buddy and his son also took a turn and it happened to both of them as well. I looked online and everything seems to point to the trigger disconnect so I opened the rifle up, but I don't see any obvious damage to or wear on the trigger disconnect. Could it be a magazine issue? I didn't think to try swapping mags until after I got back home. Any other suggestions or do I just need to take it in to a competent gunsmith?