It's occurred to me that despite consuming huge amounts of information about this prop I don't know anything about this particular piece, what it's called, or what we think it is/was.Much google-fu was unsuccessful.
That said, it was probably machined to resemble it, I'd say. Much like the sight rod was likely machined to resemble a pin vise or screw driver, instead of actually being a found part.
There was also some hope for a while that the front end cap might have been the stub of the Steyr's barrel, turned down and notched on a lathe, but the hole for the striker-like pointy protrusion is smaller than the chambering on a .22. Another one of those things you want to be right, because it would be such an elegant solution (& it's threaded for the receiver), but doesn't quite work out.
It's also one of those details in the gun that fans wonder about having a narrative purpose, like the lights, the big hole in the back of the grip, etc. Since it moves in and out with the bolt when the bolt handle is open and back, we've all wondered if there was a reason it was made that way.
I'm away from my desktop computer but my friend and I looked at numerous caps of that "pin." It is not part of the Steyr, I have a Steyr SL upper receiver with complete bolt assembly, etc. and it looks nothing like the firing pin but it is an easy assumption to make. I'll post some pics of what we machined up for it. It IS connected to the bolt assembly so when you move the cocking handle it moves, etc.