Have had brass & steel unwind from the subbase.
Have seen more brass oversized (1.375-1.379") lately too. An oversized
ring will not fit in a subbase on-spec. Steel often undersized,
occasionally right on.
Because an oversized ring will not fit an on-spec plate (like the ones
I make) I will not buy brass.
Notwithstanding, brass is pretty and won't kill carbide like steel
Using the hardware at the http://www.patwarner.com/sundries.html link,
I can tighten and center to within a couple of thousandths, perhaps a
more important factor than material choice.