metal shrinkage

As one of my first milling projects, I created a firing pin for a rifle to experiment on the length of the actual pin
that strikes the primer on the bullet. The original was piercing the primer. I had recently replace the trigger group with a new one which had a broken hammer. I figure the strength of the new trigger group hits the end of the bolt with a bit more force which causes the problem. The rifle is a bit rare so I didn't want to work on the original and take a chance of ruining it. Hence the copy. The original was 4.200 and the tip extended past the end of the bolt 0.060. I made the copy to extend 0.050. Sadly it wasn't enough. The copy also pierced the primer. At this point, the force from the hammer and the pressure of the gasses acted on the copy to make it decrease in size by 0.085. I'm guessing that the steel I used was too soft? I tried to harden it by heating and quinching but I think that will only do so much if the metal is on the soft side. Niormally the gasses won't be hitting the firing pin but did in this case becasue of the pierced primer. I'd like to make a copy that will last more than one shot so any clues as to what do?
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