Here's what Raimey had to say in a long series of posts back in '09 on Krupp barrel steel: "By the early to mid 1890s, quality gun tubes were composed of crucible nickel steel(elastic limit of approx. 62k psi) and Krupp held the secret and the skilled labour to produce it. The crucible nickel steel could be associated with "Fluss Stahl" while the "Guss Stahl" was probably plain ole cast steel with some of the required components for a quality tube but were present by accident only. Sometime near 1903/1904 Special Weapons Grade tubes(Spezial Gewehr Lauf Stahl) were on the scene and for now I suspect chromium or something of that nature had been added to the crucible nickel steel." In reading through a long discussion on barrel steel I wonder if Guss was the original "puddled" steel which was carefully mixed, poured, and hammered into submission by craftsmen and selected samples used for barrels.
