There are shotgun chamber brushes, probably just one of the bigger calibers or guages. My 12 ga chamber brush has been on a stubby rod for many years, the front is worn, but there's plenty left. Similar for rifles, the popular chambers even have stepped brushes. Leading is why I'll steer away from fibre wads, no big deal cleaning, but those might be pellets that are lost to the pattern. 22lr is a good chamber to look for build up in that area.