Since I am not working due to this virus I have been catching up on unfinished projects.
I found a CH 308 swaging die that I bought stripped and made the internal parts and needed to make a punch to see the shape the internal cavity .
I grabbed a 5/16 grade 8 hole and measured it and it was.308”!
I polished off .001” and was finished!
The shape is a round nose suitable for a 30 Carbine or maybe a 300 Blk, or maybe light 308 or 30’06!