Hello Duke,
Welcome to the forum!
That's an unusual modification to the barrel nut. I've not seen one like that before. All I can suggest is that if the Roll Pin runs straight through the barrel nut, it should be possible to drift it out. Once removed, you should be able to unscrew the barrel nut and strip it in the usual manner.
Let me / us know if that pin does go straight through please?
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Cerwyn
Hobby collector of Replica model guns and Militaria.
also member of Living History Reenactment Groups.