Originally Posted By sparky27:
I had this happen once ––-
My problem turned out to be the gas tube. I inserted the pin in the FSB "ahead" of the gas tube instead of through the pin hole. BCG would hang up at exactly the same spot. I swore it was something to do with the bolt.
Thank you sparky, that did turn out to be the case. The length of the bolt extruding from the upper receiver seemed suspiciously like the length between the gas tube roll pin to the front of the gas tube.
I resolved this by taking out the gas tube roll pin, fitting the bolt first so that the receivers would close (so that the gas tube is in place), then punching the pin back in.
thanks for all your help guys!