To address Stan's question, and marketing hyperbole aside
Titanic steel was of course a quality steel of the period, and the low levels of nickel and chromium likely increased corrosion resistance.
Dean's point is important, and we don't have an adequate sample of barrels over time, but it is likely that composition changed somewhat.
“Parker Steel” was adequate for the application, but was not considered "fluid steel" - a single sample was non-standard Acid Bessemer Resulphurized Rephosphorized AISI 1109 low carbon steel ie modified decarbonized steel.
It is well documented that the U.S. double gun makers for the most part used Cockerill fluid steel "rough forged tubes" fabricated by
Laurent Lochet-Habran , which was Open Hearth AISI 1021-1034 with a tensile strength of 75,000 – 85,000 psi
There were better (stronger and greater corrosion resistance) steels used on high grade mostly Continental doubles in the early 1900s
Krupp “Nirosta” (1912 patent NIchtROstender STAhl 21% Chromium / 7% Nickel Stainless Steel introduced in 1913): 114,000 psi
Bohler “Antinit” (Rostfrei Laufstahl chrome-molybdenum-vanadium introduced 1912): 138,000 psi
Poldi Antikorro &
Wittener Excelsior Stahl
4140 chrome moly steel was not used for gun barrels until about 1930
BTW: If someone would like to send me a chunk of their Acme or Whitworth barrel I'd be very happy to take it over the METL for composition analysis and tensile testing
