I agree the pin is probably plain carbon steel, hardened and then tempered. If this is the case, all you need to do is re-temper.
[professor hat]
The process goes like this for basic steel heat treatment - The steel is taken above its transformation temperature, usually a dull red. The standard home smith trick is to slowly heat it until a magnet no longer sticks. For maximum effect, you'd need to hold it there for upwards of a couple of minutes for a firing pin, but if necessary you can quench immediately. The FASTER the temp is dropped, the HARDER the resultant steel. Old timers used to quench in icy brine for maximum hardness, or even mercury, which can kill you, so that's a bad idea. But warpage with severe quenching may occur and this depends upon the alloy.
Oil quench is probably the safest. Once quenched, the steel is dead hard and a file should squeak off and not touch it. Think of it like glass, hard but brittle. Tempering is next. Tempering takes the glassy hard steel and turns it into a tool. It's nothing more than heating the metal to perhaps 300 to 600 degrees f. and then letting it cool. The higher the tempering, the softer it becomes, and the more shock resistant.
What this means is if the Ciener pin was tempered at 400 degrees, and we re-temper to 500 degrees, it'll become slightly softer and more shock resistant. If you go too far and it becomes too soft, you must repeat the entire cycle, which is not good, as a piece of steel the size of the pin will oxidize and flake at transformation temps. The use of a borosilicate glass powder like KeepBryte will prevent all oxidation.
That's why I like A2 steel, which is quenched in "air". The parts are wrapped in stainless foil, avoiding all oxidation, heated, and the whole foil pack is simply set out on an iron block to cool. It is then tempered like plain carbon steel, except the required tempering temps are much higher.
To mass produce Ciener pins, I'd preferably go with a handful of stock M-16 pins. Anneal the batch, avoiding oxidation. They'll be soft and can be turned and milled. Then, the whole bunch would be re-heat treated and annealed to probably somewhere near spring temper, plenty hard for a .22 and durable to boot.
[/professor hat]