This could lead to annoying problems though. I suppose it would need to drop ammo that is not for any currently carried guns first. The first idea would make more sense, but require some type of handling situation that would allow it to smartly drop extra ammo, which is where the difficulty comes in. My idea would be to limit either ammo as types: pistol, rifle, ordnance, or as individual ammunitions: 10mm, 9mm, Missile. I had an idea for making one a while back, but could not decide how it should function.
Well, now that someone's requesting one, I can ask some questions.