I found this bug the other day, that works with pretty much anything that can fit in your hands and backpack. What I did was I had a sawed off shotgun in my hands, and it resided in my backpack until I swapped my backpack, then I looked on the floor and there was another shotgun full of ammo in the bag I just dropped, and the same shotgun in my hands, I did this with my friend and we both had one and saw it, but when we shot, we shared the ammo in the two guns, and if we put the gun away it would return to the bag we took it from even from a few miles away, It's fairly easy to do and could be exploited in order to get items back on death, like leave a bag with the duped gun in it, spend all it's ammo, and if you get caught and die, just put the weapon away and it will return to the bag, which you can then go and find after respawning or something unfair like that.