First, follow James Ks recommendation, then, if you must
... Flex-Hone makes chamber hones in 400 and 800 grit for specific cartridges. They are intended to "finish" a cut chamber with a smooth, specific angle crosshatch... typically 45 to 60 degrees.
I would not suggest using these without a thorough understanding of what will happen if you use a Flex-Hone incorrectly... they can be, in the wrong hands, very "aggressive". A pretty decent thread on the subject of chamber polishing can be found here