Brent D,
Walter Grass taught me how he fire blued screws, pins, etc. He held the polished screw in a pair of long nosed pliers, and played it in and out of the flame of his propane torch. In doing this, he watched very closely the color change. When he got the color he wanted, he quenched in oil. Interestingly, he used a similar procedure for hardening firing pins. He heated to cherry red and quenched the polished firing pin. He then polished the hardened firing pin bright again. This time he held the firing pin with a piece of iron wire wrapped around it( to prevent the "heat sink" pliers would provide). He played it in and out of the flame also, concentrating on the heavier, rear part of the pin. Due to different diameters, the color will run from the heavier to lighter parts( larger to smaller).When the color runs to "Straw" at the tip, from blue at the back end. This leaves it harder at the back, where it is struck by the hammer; while the smaller part that strikes the primer, is drawn to be tough rather than brittle. This requires that the colors be closely watched. BTY, parts that were "straw" can be colored the same way as the screws, just quench when the color runs to straw. This takes less time than heating the lead pot to temp.
Mike
