Jim in Idaho
I think your method of leaving the carbon remover in overnight with the barrel plugged, lets the liquid work on the carbon. I suspicion, that applying any carbon cleaner with a patch just does not get the carbon saturated. In order for it to be removed easily, it needs to be loosened and/or dissolved.
Here is a good one for you. My shooting partner was shooting his 22-250 and had a cartridge that did not want to chamber. He tried another and the same results. Come to find out, he had a sliver of carbon come loose and lodge in the chamber. He found it when cleaning the gun.
