How to clean the inside of the bolt carrier? How to you get that caked on carbon from that hard to reach area?
The first step in cleaning an AR-15 bolt carrier group is to remove it from the rifle. The bolt carrier group can be removed by unscrewing the barrel nut and pulling the barrel and upper receiver assembly forward off the lower receiver.
Once the bolt carrier group is separated from the rifle, it can be cleaned with a solvent like Hoppes #9. Be sure to clean all of the carbon and dirt build-up from the inside of the bolt carrier key and around the gas rings on the outside of the bolt. A brush may be needed to get into all of those hard-to-reach places.
Finally, a light coat of oil should be applied to all surfaces of the bolt carrier group before reassembling it and putting it back into the rifle.