Amentum

Stability in flight was important because it allowed the javelin to land on its point, which was the only way the throw could be accurately recorded in competition or be useful against a live target.

In competition throwing for distance, including the Ancient Olympic pentathlon at Olympia, Greece, a blunt javelin would be launched at about 45 degrees, but in war or the chase, a sharp weapon was thrown much closer to the horizontal.

More recent experiments have failed to replicate this level of enhancement, with well-designed tests, showing only a 58% improvement on average.

[4] The advantages of the amentum are the high precision for fast-flying light javelins, and a less demanding construction than atlatl darts.

Italian, Gaulish, and Iberian troops used them before and after the Roman conquests, they are mentioned in use by the Medieval Irish, with the strap referred to as suaineamh,[5] and remains have been found on spears in the Nydam bog finds, where some appear to have been permanently fastened with studs.