According to the book I mentioned above, these barbed spear head come from tribes in the northern part of the area occupied by the Zande tribe in Congo (close to the border with South Sudan). The Mangbetu also have barbed spear heads. But..with Mangbetu spears the spear heads are quite small.
These were used for light throwing spears. The shaft was a simple wooden stick, sometimes with som iron banding at the end (as counter balance).
I'll put some pics of other Ngbandi spears on the forum tomorrow.
