I shot my Ar about 500 times last Saturday. Cracked her open on Sunday for the cleaning.

Cleaned everything as usual with Break Free CLP.

Noticed Carbon/powder buildup just behind the rings on the bolt. Scrubbed and scrubbed. Still nasty. Soaked overnight in Clp. Scrubbed some more. Still nasty. Soaked overnight in Hoppe's. Scrubbed some more. Still nasty.

Any Suggestions?

Should I scrape it off with my pocket knife?

use a steel or brass brush..

Armalite has said not to over clean that area. Check out ther faq's. I use hot water and soap, then blow it off with compresed air and coat with clp. Does a great job

Quoted: Armalite has said not to over clean that area. Check out ther faq's. I use hot water and soap, then blow it off with compresed air and coat with clp. Does a great job

Correct. The carbon build up is self-limiting. It won't hurt the functioning of the rifle.

Simple green and flush with water, recoat with clp....
Robert

Quoted: Should I scrape it off with my pocket knife?

NOOOOOOOO!!! Don't do that.

I would just get what easily comes off the tail section of the bolt with CLP/RAG and let it go.