A friend of mine brought in a Sabre barrel that had been messed with by a mechanic who goonsmiths on the side. He/they ruined the upper by rotating the barrel without first removing the barrel nut. Long story short...the barrel pin (if thats what you call it) is missing now. Can one turn down some round stock and press it back into place or solder it. I've never seen a barrel without this pin. What do you guys think?