Howdy
As usual, Pettifogger is right on the money when he talks about heat treating. It is heat treatment that makes most of the difference when talking about the strength of a cylinder.
This really makes the case for buying a geuine Colt, as they heat treat the barrels and cylinders. I have the specs for the cylinders right from the factory and I can assure you that they are heat treated. You DO get what you pay for.
JP, are you sure Colt is heat treating their barrels? I kind of doubt it. With a revolver, the cylinder is the pressure vessel that is most likely to fail if there is an over pressure event. The thickness of a barrel wall makes it much stronger than a chamber wall and heat treating a barrel is not necessary. Most revolver failures involve the cylinder bursting, it is quite rare that a barrel bursts. Heat treating a cylinder is very important to insure the strength of the cylinder when fired with modern Smokeless Powder loads.
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Don't sell iron short as a metal used in the manufacture of firearms. Also, don't confuse cast iron with malleable or wrought iron. Cast iron is full of impurities, and is therefor of little use in firearms manufacture. Cast iron is fine in compression, and was used as a building material through out the 19th Century, but it is a poor choice for applications that will put it in tension or shear. Malleable iron, on the other hand is quite strong and took the pressure of Black Powder firearms for centuries. The Springfield Armory cranked out many thousands of muskets for the Civil War, and they all had iron barrels. Malleable iron is purer than cast iron, most of the impurities, including carbon have been driven out, and it can be formed by forging. The Village Blacksmith with his forge and his hammer was working with malleable, or wrought iron, not cast iron.
Most of the percussion revolvers had malleable iron cylinders and frames. Up until about 1883 the Colt Single Action Army had cylinders and frames made from malleable iron. After that, low carbon steels were used, and by 1900 Colt had perfected heat treating medium carbon steel frames and cylinders enough that they felt confident factory warrantying the SAA to be used with Smokeless Powder.
Although steel has been produced for over 1000 years, it was only available in small quantities and was expensive to produce. The Bessemer process, developed in 1858, made mass production of inexpensive steel possible. The Bessemer process started with pig iron (cast iron). The iron was heated in a converter with great quantities of air pumped through the melt. The oxygen in the air combined with impurities in the iron, including carbon, driving all the impurities out of the melt. Then a controlled amount of carbon was reintroduced to the melt to create steel. But steel made by the Bessemer process tended to include small bubbles and cavities as a result of the turbulence created when the air was pumped through the converter. It was not until about 1874 that Sir Joseph Whitworth developed his method of producing steel ingots under hydraulic pressure. The pressure compressed and eliminated the porosity that had plagued early Bessemer steel. Whitworth was the same man who developed the Whitworth rifle with its polygonal bore. His hydraulic pressure method of making steel went by several names, Whitworth steel and it was also called Fluid Steel because of the hydraulic connection.
I do not know this for certain, but I suspect it was the development of the Whitworth process that finally convinced Colt to produce the SAA with steel cylinders and frames.
Modern standards for steel are international, Italian gunmakers use the same standard steels as anyplace else in the world. Many modern firearms manufacturers use 4041 steel for high strength applications like cylinders.
http://www.simplytoolsteel.com/4140-alloy-steel-data-sheet.htmlBut trying to pin down a manufacturer as to exactly what steel alloy they use is probably not going to be successful. Most will treat that as proprietary information and will not divulge exactly what alloy they use. I once called up Ruger and asked what Stainless Steel alloy they use. They would not tell me.
But the bottom line for strength with any modern oil hardening steel will be to heat treat it.