Yes, the nut is going in the trash no matter what. I have a precision nut from Jim ready to go. As far as why it wont fit, I dont think its major or minor diameter, I think the splines are just a little off. Not sure if its shape or placement. It's really close, enough that you think tapping it with a mallet will do it but it won't. I've been worried the pipe wrench will slip and mess up the barrel but maybe some duct tape to protect it?