Research into porcupine quills shows that the barbs at the tip not only make the quills harder to extract (something we probably all know) but also reduce the resistance to penetration.
http://www.bbc.co.uk/nature/20628302 (http://www.bbc.co.uk/nature/20628302)
"And I think [we were] most surprised to find that not only do the backwards-facing barbs make the quills difficult to remove, they significantly reduce the penetration force.
To our knowledge this is the first demonstration of a highly engineered system that achieves polar-opposite dual functionality."
The reduction of the force needed for penetration is the interesting aspect. If this works for porcupine quills, one suspects it would also work for arrows and, for that matter, barbed throwing weapons such as the angon.
Patrick