JTR - I absolutely did not mean to refer to Ravenshear as a "wannabe frontiersman", I like his work & now & again have referred people to it. He can take a technical subject and translate it into words that can be used in one's home workshop. I appologize for any misunderstanding.
As far as the size of my own ego I have no problems with your comment & accept it as a complement.
I really should not comment on metallurgical items here.
Metallurgy has been my profession for a good half-century now. I do tire of seeing fine craftsmen use the worst grades of steel they can possibly find and heat treating them without any background from knowledgeable men such as James Howe or Kit Ravenshear. All this does is raise my blood pressure and irritate those who . . . enough.
Beginning in the late 1960's I had occasion to communicate with the finest metal craftsman in the US. One could weep looking at the beautiful, but broken, springs he sent now & again. I never succeeded in getting him to temper those nice modern steel springs hot enough. Last one I saw he found a local source for strip in, I believe, 1095. Appropriate steel but the strip was made for a specific end use, by a process that left a defect or so that probably wouldn't have mattered for the intended product but did mess up a fine mainspring.
Steel is much cheaper than the hours you spend working on it. Stay out of the scrap yard. Buy something, preferably made in USA or Europe, from you favorite on-line dealer. Then you know what you have (unless it came from a popular Asian source).
So my final preaching - do not use 18th or 19th century heat treat methods with 21st century steel. They do not always mix well.
You cannot get traditional steel anymore. Well, in theory you can get some current production British wrought iron and deeply case-harden ("cement") it to make blister steel, which you can then break, bundle & forge into shear steel, from which you can make a typically so-so traditional spring.
Or you can assume you are gonna copy a 19th century "cast steel" spring and buy the nearest thing, that being probably 1074 steel. Actually that is a god choice, as it will tolerate quite a bit in heat treating & still make a decent spring.
But I am going astray. Someone told you that O1 is better, well "better" in what way? So you make a lovely O1 spring & then heat treat it as some Wannabe Frontiersman says and it breaks. Yup.
I'm sorry guys, I have no business commenting here. Sad to say, you do live in the 21st century and must, for the most part, deal with 21st century metal. Get thee Ravenshear, or Howe if you are brave.