There are several variations of the 300 series stainless steels besides just 304 which are of the 18-8 class. All of these are non-magnetic. Machined a pile of these when I worked at AEDC, TN as we had one test facility that everything which went inside was required to be non-magnetic. For the most part it was either aluminum or one of the 18-8 series, depending upon strength requirements.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra