The Slingshot Channel wants to make a Zombie Movie, that's a fact. The trailer for it is all filmed and will be published shortly. This means that lots of post apocalyptical slingshot weapons and ammo has to be made, in order to use them later on in the movie.
This time, a major concern in Zombie hunting is addressed: How much brain do you actually have to destroy to put the ghouls to rest for sure? Clearly, Zombies only need a small part of their gray matter. Broadheads would work really well once inside of the skull - but those aren't very good bone penetrators. Field tips or bodkins will easily pierce a skull, but won't destroy much brain matter later on.
So a new arrow tip was made, from scrap iron and cheap steel angles. The simple mechanical trick lets the arrow pierce the skull just like a bodkin, but then sharp blades swing out and cut a lethal pathway through the bug infested, decaying Zombie brain.