Don't use stainless steel brushes in bores or chambers.
These are for use on guns so badly neglected, you have nothing to lose.
The Brownell's BRONZE chamber brushes work faster and better then over-caliber bore brushes.
The chamber brushes are not only over-size, they're also made of a much stiffer bristle than bore brushes.
These make short work of cleaning fouling from chambers, and there's no risk of damaging a chamber.