316 (A4) would be a marine grade stainless for fittings on boats used in salt water, 304 (A2) maybe ok for fresh water. 416 that is used for rifle barrels and actions can be heat treated and machines nicer. I don't think it makes sense to try use 316 on a rifle. Think the Germans developed the 304/316 grade in ww2 called it VA 2&4 Stahl, Versuchsstahl.
My take, 416 needs a bit of time to wear in and let the chrome on the surface oxidise. Rub down with a oily cloth every now and then, it will rust less and less.
edi
My take, 416 needs a bit of time to wear in and let the chrome on the surface oxidise. Rub down with a oily cloth every now and then, it will rust less and less.
edi