I am becoming more convinced that these, indeed, may be crossbow 'bolts'.
The European crossbows tend to have smaller 'prods' (bow part) than Ethnic made ones. This is due to the materials that the prod is made. African crossbows I have seen have prods almost the same size as a normal bow...which would need the 'bolt' to be longer than the average European crossbow.
Perhaps the leather flights are better suited to a crossbow....more wear resistant and less affected by any moisture on the stock of the crossbow(feathers would clump up)
Regards David