When comparing steels used for gun barrels and knives, or, for that matter, any stainless steel that can be heat treated, are actually somewhat rust resistant.
By this I mean, Stainless barrels and knives will rust, but they are more rust resistant than non stainless. That is because so called stainless, as used in firearms and knives contain from about 14 to 17 percent chrome.
Stainless used for structural purposes and kitchen ware contain upwards of approximately 19-20 percent chrome.
