As a heli crashsite changes, the server despawns the items around and inside the heli. The radius of this function seems to be atleast 75 meters. Recently lost two weapons that I did find on that chopper site. I dropped them about 75m from the crashsite and 20 seconds later they disappeared along with the chopper. So I had moved those weapons and modified them (added mags, removed scopes). I do no think this could be intended.