Arrows kill by pushing a sharp cutting edge through the animal, which sets the stage for massive hemmorhage. Dull cutting edges don't cut, they just push the meat out of the way. Like when we saw away at a raw piece of meat with a dull knife.
Small game blunts? I dunno exactly how they kill, won't be blood loss, though.
Ya know, Indians made iron arrow heads, too. Might be fun to take "found" sheet iron, and try your hand at making iron broadheads, too.
Good luck with this. Sounds like you'll have to have lots of patience.
Blunts kill by blunt force, I guess. Same as a slingshot. As kids we used to cold forge nails into points for arrows and blowgun darts, depending on size. I actually have access to a bunch of barrel hoops which used to be wrought iron. I'm not sure what they are now. Appear to be mild steel. That'd be a good approximation of iron. May gove that a go, but I need a good primitive bow first, so that's the next project.