I like it!  Ductile.  Hard.  Strong.  Exactly what's needed.

WOW!! "Ask a simple question..." 

Fitzie, it looks like you are my winner, although John Taylor's car trunk spring stock entry runs a close second.  I will be sending you (FITZ) a PM about the time you get back home with dimensional info, and will probably make one out of spring stock as well just in case.

The rest of the story;  This firing pin looks a lot like the ones you see on any number of shotguns and single shot hammer rifles.  It is just a cylindrical piece of multiple diameters with a square notch milled across for the retaining screw.  The "flies in the ointment" are that all dimensions are relatively longer, the notch is rather deep and cut in the smallest diameter of the pin (except for the firing pin protrusion itself) and the 1873 Model design keep a big old percussion style hammer that really whacks the whole thing rather smartly.  With most pin failures, however, we see a breaking off at the point where the very long protrusion comes out of the nose of the pin, a situation that would be cured by Westerner's recipe, but since this particular one broke at the front of the notch, I suspect other dynamics involved and asked for a good alloy for the whole pin.  I think that the  17-4 PH and car spring both look hopeful based on what I now will have access to, and if they both fail to make the cut, I'll probably have to go looking for one of the exotics like the beryllium alloy suggested by DWS. As a side note, I wonder if old Doc Maynard had all this stuff to deal with, and if not, why not? 

Thanks again to all who responded,
Charlie Shaeff
aka the Green Frog

I am a machinist and have worked with many tool steels as well as just about everything used in aircraft.

First, a caution regarding Beryllium. Wear a very good resperator. That stuff can kill your lungs!! Even just making a firing pin. I've always refused to work on the stuff.

Next, I offer these things, S-7 is a shock resistant tool steel (used in such things as air hammer tools) and it might be the answer.

For other air harding tool steels H-10 thur 13 are very ductile. I think A-2 and D-2 would be to brittle.

303 SS might be ok, too as well as the case hardened 1010 steel, be carefull not to over do the firing pin tip area or use a insert for the tip.

Making sure the hole is straight, with no taper and concentric with the firing pin tip is extremely important to rule out any bending moments.

Lots more to consider,

Frank

My Mom could chew nails and spit. She used to tell me that a lot. Mostly when she was mad. I dont think a nail will work. To soft.
I think maybe Doc Maynard and all the others are rolling in their graves with laughter.
Or maybe they're impressed with all the high tech stuff we have now.

Happy Independence Day!!   

                    Joe. 

It's the square notch that's the problem. Creates a stress riser at the corners leading to early failure. Make it round to match the pin, however you can ... ball endmill, file, whatever. And yeah, polishing it won't hurt either.

Joe wrote:
Quote:
         Couldn't help myself.  

Green Frog, 
Just a curious question here:    Has anyone come up with a value on how hard (Rc) the Maynard breechs are?

Maybe a cryogenic treatment would solve some problems, of breakage.

Thanks John
I thought so.
Tom
I think Hastaloy would make a great pin if you had the tooling to work it. Good for extreme high temperatures also