I have heard of chambers being fluted. I have not seen one yet.
I recovered some brass at the range today that had what appeared to be flute marks down the side. There was a lot of blowby down the sides of the casing where the supposed flutes were. Crud was badly deposited in the rim recess. It made a mess of the brass, it can't be that great on rifles either. Looks like it would be a major maintenance nightmare. Anyone have any information on this and why anyone would do this to a rifle?