There are gas nitriding processes now, that work as low as 850°F.
High performance automotive engine valve springs are often nitrided. Corrosion is not an issue, but the nitrogen atoms penetrate the metal crystals and leave a very high residual compressive stress - which is a good thing for fatigue life. It's a similar, or even better benefit than you get with shot peening, even though the hard layer is only .001" or so deep.
I have a Daniel Mk12, that has the forged stainless, nitrided barrel. Still working with it as far as finding best loads but it seems to be at least MOA or better, and I doubt I'll ever wear it out.
