Way easier to get someone to mill off the last bit of thread on the barrel than to cut thread in a receiver.
Just take it to any machine shop and have them turn down the last thread.
Be like a 5 min job, but they'll probably charge you a 1hr minimum, so 60-80 bucks.
Also, take that screw out! Cosmetically it's ugly as S$#! and as John said, COMPLETELY useless.