Now & again someone comments on Ravenshear here. I have read and re-read his book, & offer my opinions.
For anyone planning to make lock springs, I urge you to get a copy of Simplified V-Springs by Kit Ravenshear. Read it. Study it.
Make - and - break springs, until you get the hang of it. It is a learning experience. If your first spring works out well, there is a fair chance that #'s 2 or 3 will not. Eventually you can get it right.
I am a metallurgist, with a good half-century experience with steel and nickel alloys. A fairly lousy craftsman myself, my only V-spring experience has been for miniature flint & percussion locks. I was able to cold form those springs of some nice annealed stuff Frank Mittermeier called "Swedish Spring Steel." By accident most of them worked.
A number of guys on this site have years of experience making good V-springs. If you can learn from one of them in his shop, great. Otherwise, Ravenshear is the absolute best - maybe the only - published information on all phases of spring making. This, in my not at all humble opinion.
Don't know that I can add anything useful to what the late Mr. Ravenshear wrote. Well, I might say that investment cast springs, and most investment cast lock parts, are often made of some alloy steel. This is because alloy steel (e.g., 6150, 4140, &c) makes a better casting than does just plain carbon steel 1018 or 1095. I don't know why - ask a foundryman.
To make an investment casting, the molten steel (at about 2850 - 3100°F) is poured into a hot ceramic mold. That lets the molten steel flow into every tiny part of that mold, even permitting cast-in engraving. It also means the steel freezes and cools very slowly. The result is an enormous grain size. Yeah, this is my industrial experience, as well as text-book metallurgy.
Large/coarse grains are very bad, tend to make the steel Widgit likely to break. Fortunately, with steel one has the possibility of making these grains finer again. This is done by heating the steel to a hardening temperature, somewhere between 1450 and 1650°F, then cooling it. Depending upon the steel one might air cool it, though it is probably better to bury it in ashes or sand to cool very slowly.
If you don't care for how I said it, read Simplified V-Springs.
