Parkinsonsd,
"Ringing the chamber" is damage to the chamber of a gun barrel, particularly a large-caliber BP barrel, caused by partial chamber obstruction or a cartridge case too short for the chamber.
The resulting bulged ring in the chamber causes difficult extraction when using full-length cases.
In the case of partial bore obstructions, that is most likely to happen from using dacron fluff or fiber or cardboard wads in smokeless powder loads in bottle-necked calibers smaller than .45, although documentd in larger calibers exist. The NRA Technical Advisor strictly recommends against using any synthetic filler material in smokeless powder loads for that reason.
In the case of black powder loads, extensive firing using shorter brass (.45-70 in a .45-90 chamber) causes erosion of the chamber/throat area and subsequent firing residue accumulation becomes a partial bore obstruction. Both can be avoided with diligent cleaning.
HTH
John