I’ve used large patches through a loop for many years and they do a pretty good job of getting into the recesses. My loop is on a thick, steel, surplus caliber .50 cleaning rod that lets me exert some side load, forcing the patch behind the locking abutment. About once per year, I pull the barrel, properly clean the action and either replace or reinstall the barrel. This only applies to actively competed rifles that see over 1000 rounds fired per year. In between, I inspect them with a bore scope.