From your similar post on another forum, my response:
There's two ways to clean AR bolts and bolt carriers of carbon fouling: Mechanical and chemical.
Mechanical methods use scraping tools like the Magna-Matic, C.A.T. 4 tool, or the other tools that clean only the bolt or only the bolt carrier.
The chemical method uses a dedicated carbon removal chemical like the excellent Slip 2000 Carbon Killer.
The easiest method of using this is to really shake the jar, then drop the parts in the jar and let soak 15 minutes.
Remove and brush. If the parts are still carboned up, soak another 15.
This works very well because it gets into places the scraping tools may not be able to reach, especially in substandard parts that have a lot of machine marks, and the liquid gets into the gas key on the bolt carrier.
Either method will do what's really needed, and that's to remove the carbon fouling from the critical areas that might cause malfunctions. Even if not every trace is removed, either method will be enough.