The firing pin really has nothing to hang up on and i would bet that your extractor/ejector is causing the problem
Actually, a firing pin that does not retract due to a bad spring can hangup on the lower section of the barrel/monoblock as you try to open it. (Had that happen on one of my guns). While I don't think it is the most likely cause, it IS a possibility
This happened to my old gun and I had to put a thick dowel down the barrel to push the firing pin back in.