Machinist Question

[Bonc_CHL]

I am a machinist by trade and just happen to like guns also, so here is my question.....
I have an older Hi-Standard Model B .22cal and my firing pin has broken due to it not being cleaned well over the years when my grandfather had it.
So I am so inclined to machine my own for it out of Titanium in my down time at work, is this illeagle in any way shape or form? I can't find a logical reason in my head why it would be, but I know the fellas at the good old ATF and I differ on things from time to time.
If possible please provide where you got the info.
Thanks

[apostate]

There's no problem with doing so for personal use. You could even machine an AR lower (or complete firearm) for personal use, although the frame would require a serial number IIRC.

[Chemist45]

OK, when I read this I was thinking "Now why would a titanium firing pin be illegal?"