All of the following using the new (to me) hammer die on test metal…
(Image 1) Tapered to square.
(Image 2) Tapered to octagon.
(Image 3) Tapered to hexadecagon.
(Image 4) This is as facet-free as I can get it using the flat face of the die (someone with better power hammer kung-fu could probably do better…).
(Image 5) A lot less faceting using the rounding surface of the die (probably hard to see here). So… success!
Square 
Octagon 
Hexadecagon 
Tapered with flat face of die 
Tapered with rounding funnel on die