Question; my M&P has a stainless steel barrel and slide, are all the other metal parts stainless too? This may have been answered elsewhere, sorry if so. AND - What about stainless steel revolvers, are all the metal parts stainless?
I highly doubt all the internal metal parts are stainless. A magnet test won't help, the stainless they use for barell & slide is magnetic (assuming it's actually stainless). Same for stainless revolvers, you'll likely find parts inside that aren't. I would think that certain parts, like springs, will be made of the best material for function, not corrosion resistance. You probably shouldn't be dunking your pistol in salt water regardless.