My dear friend and savant in the field of firearms and trigger design Robert would say:
Except for Lothar Walther all others use similar corrosion-resistant steels (the term Stainless is misleading for the 400 series steels), and it is typicaly the AISI/ASTM/SAE 416R
SS 416 is the material of choice for barrel makers not due its qualites as barrel steel but due to its machineability as it alloyed with sulphur .A blessing for the machinists, but handicap to the qualities one should normally expect from a barrel steel: 416R is Quite soft,exibits higher than desired friction ,is prone to pitting… But it polishes so well ...LOL
Lothar Walther uses a different alloy, AISI 420 (EuroNorm X20Cr13 ,W/Nr 1.4021), with slightly higher Carbon (0,20% as opposed to 0;12% of the 416) and Chromium content (13% as to 12% of the 416), but no sulphur addition, which possess all the properties one could ask for a barrel steel.Steel is manufactured to LW specs by a single crucible Boehler-Udderlohn from Austira .
Their ‘savoir-faire” is unique, and they are the only ones capable of using this alloy for barrels in industrial capacity a process mastered over multiple generations. LW50 -> 420 It might well not be much liked by smiths who have to machine it for chambering and threading, but, quality-wise, the result is certainly worth the effort and shouldn't be a problem for a competent machinist
Does this make a better shooting barrel? Not on account of material. Longer lasting? the answer is ‘yes’….
Lothar Walther is probably the worlds largest manufacturer of precision barrels by a considerable margin.
Material properties:
-The 416, supplied in annealed condition, is about:
Brinell Hardness : 170
Rm: 630MPa
Modulus of Elasticity: 200GPa
Thermal conductivity: 25W/m-k
-While the 420 is:
Brinell Hardness 205
Rm: 725MPa
Modulus of Elasticity: 200GPa.
Thermal conductivity: 25W/m-k