So “spring control” wouldn’t even be effective...
Wire Control! We need Music Wire Control!
Most springs are really easy to make, once you’ve been shown how it is done and you have the correct steel.
You need a high-carbon steel - 0.70% to 0.95% - or AISI 1070 to 1095 steels. You need to quench them, then temper the steel to the right point, and you’re done.
Music wire and helical springs are just so easy, they’re hardly worth mentioning. But making the main spring for something like a revolver or a side-by-side shotgun... not difficult, once you’ve learned the secrets of how to deal with steel.