I do use O1 for springs, the carbon content is roughly the same as for 1095 but the addition of chromium, vanadium and nickel makes for a (theoretically) more shock-resistant part. O1 is easier to find in thick sections than is 1075 or 1095 (at least around here). O1 can be forged but it must be done at or above 1500 degrees Farenheit and annealed after forging. Heat treating (harden and temper) is similar to 1095. I usually use o1 for springs that are a single leaf design or that have large lugs/projections, like the combination mainspring/cocking lever here which has a pivot lug that engages a pocket in the hinge pin.