Yeah, my bore comes clean after cleaning. If it's not coming out with a bore brush, or bore snake, or any of the other methods you mentioned, it's NOT a thread or fiber. If it were, it WOULD come out. If it's a crack or a scratch, think twice about just running to the range and "Blasting it out". Anything obstructing the bore can cause health issues.
edit: This is probably a good example of when to visit your friendly local gunsmith.
Just my $.02...
Last edited by alabaster; 10-14-2011 at 14:00..