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Probably the wrong place for this but there seem to be more hits here than elsewhere..... Barry made me a new longer firing pin for a ZB 26 so as to shoot the ??? (furrin') 8mm ammo with the very deep primers. Now I need to know how to heat treat it so it will last as long as the original has....... it is .300 at the big end, about .150 at the small and 3 1/2 long, 4140 material.
How do I properly harden it??? PJH
Send it out for hardening at your local place, you'll have about a 45-50RC part. Should last a long time.
Dimitri
4041 is a very heat treatable steel but you need to lookout for two issues:
1/ Distortion, due to heat treatment process.
2/ Brittleness, due to leaving the firing pin too hard
Method:
Heat firing pin up to a uniformly bright cherry red colour (you are going to need a mapp gas touch to due this, propane is not hot enough). Hold at this temperature for a couple of minutes to let the metal soak. Now plunge the pin vertically ( not at an angle, as this will produce distortion) down in to a can of oil (motor oil OK). Move the pin around in the oil to make sure of uniform cooling. Once cool, clear the pin with fine emery cloth to regain a bright steel finish.
The pin is now hard (and would break in use) and must have it temper drawn. To do this, apply the gas touch at some distance from the pin tip. You will notice that as the metal heats up it changes colour ( first yellow, then light blue, then dark blue and so on through to dark red). These colours run along the metal from the point of heating. As soon as the blue colour reach the tip of the firing pin, plunge it once again into the oil. Your pin should be now hardened and tempered.
Before you harden and temper your firing pin you should practice on scrap 4041.