Feed Rate all depends, on what tooling you are using, Carbide, HSS, long short, depth of cut, how many flutes, riggedy of your mill etc.
I sometimes go as fast as 16"min.or .2" min.
See, if you can mill {rough out with a roughing millingcutter first, the 304 is not bad cutting, in the 3....series, just make sure, you are not overheating, lots of coolant.
Konrad