if not enough wpf you cannot take your pretty ammunition, too bad! wear less armor or respect to a built with more wpf in throwing or less pt.
Thing is, i can pick up franciscas from other persons, as well as javelins. And when i use the javelins i can't pick them up...weird. :O
Edit: Heavy Axes, Javelins, Franciscas, War Dart...everything works except the jarids. And i get that message everytime.