Has been my impression that a rifle's chamber should be smooth and shiny like a mirror - others have said to be able to see some cross hatching on the finish in there - however, clean and dry - no pits or debris - the case upon firing is going to swell up to match the chamber wall - tightly - and should relax a smidgeon - to be able to extract - any rust or pits in there will cause the case to conform to that - results in a mechanical "lock" to be overcome, to get that case out of the chamber.
I've seen chambers that look like frosted bores not cleaned after corrosive ammo and the fired cases extract smoothly.
Last week I looked at a chamber that had rings from the mouth of the chamber to the shoulder. It was in 308Win and it extracted fired cases fine.
The biggest issue is with badly pitted neck areas IMHO.