For anyone wanting to make springs, here is something you should remember... Shoot for a final hardness of around 42-45 HRC. Adjust your heat treat process depending on material used to reach this hardness. This involves adjusting tempering temperature. For example, O1 will likely need to be tempered around 950F or so.
I hear of many different methods people use for temperaing, but often these don't make any mention of material being used. A particular process MAY be appropriate and work for one material, but not another.
Jim