This is how i create the arrow and fire it:
EntityTippedArrow e = new EntityTippedArrow(world, pos.getX()+.5, pos.getY()+1, pos.getZ()+.5);
e.motionX = (Math.random()*4)-2;
e.motionZ = (Math.random()*4)-2;
e.motionY = 1.0F;
world.spawnEntity(e);
The way the bow does it, it calls the shoot function, i also tried that but to no avail.