Hi Lee,
Although it's a pain to work with, I use 304 for bolsters so I don't have to heat treat it.
The American Iron and Steel Institute has a good read on stainless steel.
Referencing:
http://www.nickelinstitute.org/~/Med...ning_9011_.pdf
Quote:
"For example, Type S17700 has a machinability rating of 45, in comparison to Type 416 stainless steel at 100 percent. The corrosion resistance of these steels in the hardened condition is about equal to that of Type 304."
I suspect a lot of makers are unaware of this and put 416 into service in its annealed state.
Dan