I have a 1993-94 - 700 SS Remington. A magnet will not grab to the bolt knob, but when put to the bolt itself it attracts slightly, Do not know if it from the bolt body itself or the spring inside. The bolt has shown no signs of rust on 5-10 day moose hunts in Ontario rain over the years. If you have the action take the serial number and call or E-mail Remington they should have records that would help you.
On all of the stainless 700 actions, that I have worked on, the bolt bodies are non stainless, while the bolt handle is stainless. Magnets are not a good test as some stainless is magnetic and some isn't.
They all should be stainless. 416 Stainless is magnetic so a magnet will not tell you. The best way
to find out is to apply some cold blue in a small inconspicuous place and it will not do anything if it
is stainless. If it is chrome molly it will color.