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The "Southern" blow up 1908 Hunter Arms �Armor Steel� barrel is non-standard AISI 1018 with slightly high phosphorus and sulphur. It was not tensile tested.

Drew:

For those of us who couldn't buy a clue when the subject is metallurgy, what does that mean in terms of strength/barrel integrity?

Thanks.

Rem

A long version is here
https://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit

Summary of �Cold rolled� barrel steel tensile strengths. All can be heat treated for different applications (rifle receivers) to much higher strength, and yield strength matters also.
AISI 1005: 40,000 psi
Twist and Crolle Damascus: about 55,000 psi
Winchester Standard Ordnance and other "cold rolled" Bessemer/Decarbonized steels and AISI 1020: 60,000 psi
c. 1900 �Fluid Steel� (Siemens-Martin & Krupp Open Hearth Steel AISI 1021-1034): 75,000 � 85,000 psi
AISI 1140: 85,000
Krupp Fluss Stahl (Homogeneous Fluid Steel) was introduced about 1890 and by reported composition was similar to AISI 1045: 85,000 psi.
AISI 1040 (and modified), Bohler �Blitz�, 4140 Chrome Moly (not used until after 1930s): 95,000 � 100,000 psi
Winchester Nickel Steel and Marlin �Special Smokeless Steel�: 100,000 � 105,000 psi
Remington Ordnance Steel: 110,000 psi
Krupp �Nirosta� (1912 patent NIchtROstender STAhl 21% Chromium / 7% Nickel Stainless Steel introduced in 1913): 114,000 psi
Winchester Proof Steel (probably AISI 4340) introduced in 1931 for the Model 21: 115,000 - 120,000 psi
Krupp Spezial Gewehr Lauf Stahl / 1895 �Special Gun Barrel Steel�): 138,000 psi
Bohler �Antinit� (Rostfrei Laufstahl chrome-molybdenum-vanadium introduced 1912): 138,000 psi

Phosphorus increases strength and machinability, but can embrittle steel, esp. if cold (ie The Titanic).
Sulfur increases machinability, but if high Sulfur/Manganese ratio leads to Manganese Sulfide inclusions.
Nickel & Chromium increase corrosion resistance and hardenability.

I think we have good data that the Belgian produced "rough forged tubes" used by U.S. double gun makers prior to WWI were mostly AISI 1018 - 1030, possibly rephosphorized, with Decarbonized Steel on lower grades.

Modern alloy steels are harder with greater corrosion resistance.

Turn-of-the-century U.S. maker barrels were proved at 15,500 - 17,500 psi and were designed for shells with pressures similar (and the 1 1/4 oz. 3 1/2 Dr. Eq. Smokeless Powder greater) to today's loads.

Ordinary steel is a mixture of iron & carbon. Steel does not generally respond to hardening until around 30 points of carbon are reached.

30 points = .3%. Thus for every 100 lbs of iron, there would be about 4.8 oz of carbon. With a 20 point steel, there would be about 3.2 oz of carbon per 100 lbs of Iron.

Annealing, Normalizing, Hardening, etc are all forms of Heat-Treating. These barrels of 20 points or less of carbon "May" have gone through some form of heat-treating, but they were not "Hardened".