17-4P.H. H-1150 is the BEST material for your guide rod.
Background: Not all Stainless Steels are created equally. There are three types of stainless steel alloys in common usage. The 300 series or austenitic commonly used in flatware and fasteners is highly corrosion resistant but not very strong or hard. The 400 series of stainless including martensitic and ferritic commonly used in knives, razor blades and firearm parts are tougher and harder than the 300 series. The downside is due to additional carbon, 400 series alloys are LESS corrosion resistant than 300 series. The third type are the Precipitation Hardening alloys. These alloys combine the excellent corrosion resistance of 300 series with the ability to be hardened, the best of the other two series combined!
Steels are typically heat treated by bringing them to a certain temperature and quenching them in a manner that retains a hard or tough grain structure.
Copper alloys and some 300 series stainless can become hardened by working them either by bending, hammering or otherwise forming the material.
Precipitation Hardening alloys rely on low amounts of heat over a matter of hours to allow the alloying elements to precipitate into the grain structure in a way that increases the metal’s hardness.
The H-1150 temper brings 17-4 P.H. up to 34 Rockwell C scale.
Bottom Line: 17-4 P.H. H-1150 is the ideal material for your STA-TITE guide rod because its hardness resists the spring’s attempts to scratch it while not being “glass hard” or brittle. It also ensures that small threads have plenty of strength to withstand repeated dis-assembly/re-assembly without stripping or galling as can occur with softer stainless alloys. If the cosmetic black oxide treatment is scratched, the stainless will continue to resist corrosion better than any 400 series stainless or alloy steel.