Here is a punch I made. I went a bit overboard with cutting the center out, but it works as well as any of the others and shows the edge a bit better.
Is this how Lathesmiths GC punches are made? I don't use many PB bullets so I haven't tried to size PB bullets with this type of punch so don't know how it would work. Might cause problems without a GC.
I do know that the punch should be pretty close to the bullet diameter, just enough so it doesn't interfere with the die, like maybe a couple of thousands under size of the die.