Unrivited javelin heads

[M. Caecilius]

Would this account for the large numbers found at the recently found late Roman battle field in Germany?

Which battle field do you mean?

I'm not quite sure whether you mean that javelin heads were found on their own, rather than with the shaft, but in that case, it's probably a matter of the wood having rotted away. You'd need a closer look at the heads to see whether there are remains of wood still attached to them.

Otherwise, I've had a number of arrow-heads come lose in a target and once or twice without me really knowing what happened (just seeing the arrow bounce on the target, with no trace of the head), so I can't say whether they dropped in flight. As Demetrius says, it seems unlikely as there is no real force, unless it happened straight at the release. Of course, none of these heads were riveted, and overall, they were quite well done. I assume what happened to these arrows might also work for javelins.