The aftermarket barrel nut that wouldn't thread was the one removed from the previous barrel. It threaded on the previous barrel easily. I also tried a new aftermarket nut purchased fairly recently that would not thread. Difficulty threading the barrel into the receiver was a first for me. I didn't have the nerve to pursue sanding the barrel tenon until it fit. I usually hand tighten the action wrench and tweak it with a wrench. It surprised me to find that the barrel would not thread in without loosening the bolts. I started this thread for information purposes for others that may come across the issue. I thought about the problem for a couple of days before proceeding. Thanks for the feedback.