Well, the vanila bow enchantability is set to 1 so this also was what my bow's enchantability was set to, I tried to set it to 22, no diffrence, still only unbreaking applys to it.
btw, the reason I asked about the registering of the item is that I remmeber RWTema (The author of Extra Utilites) talking once about the same problem: his sword wasn't enchantable, and when he fixed it he said that the problem was that the sword wasn't registered as a sword but as a item that heppend to do a lot of damage