Replacement: A.H. Fox introduced Chromox High Pressure Fluid Steel (chrome-nickel-vanadium steel) for graded guns in 1912, but analysis of a c. 1929 Sterlingworth Fluid Compressed Steel barrel showed it to be AISI 1040 with a measured Tensile Strength of 103,000 psi; similar in strength and hardness to non-heat treated 4140 but certainly less corrosion resistance. Modern steel loads do have a thick protective shot cup, but I would not use the loads in a Sterlingworth.

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