Cleaning the AR Bolt Carrier
The trouble with scraping tools is that the bolt carrier's hole where the bolt is inserted into is not necessarily machined smooth. A scraping tool will only clean the surface it contacts and not the grooves it cannot clean.
I dumped the bolt carrier into a ultra-sonic bath for 20 minutes. I soaked the same bolt carrier overnite with a Hoppe's saturated cloth. I even scraped at the bolt carrier with a bamboo BBQ stick.
I destroyed an old 45 caliber handgun brush scrubbing at it; but success was limited as the bristles faced the wrong way.
I finally found a dremel brass wire brush whose bristles faced forward. Perfect, except that the dremel wouldn't reach down that far. A scribe with a removable tip was found and the tip removed. The brass wire brush was secured in it and the scribe body placed in a drill press (and later a lathe). Turn on the press and hold the bolt carrier up to it and it cleaned up rather nicely.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!