I was playing Dayz with a friend. We found a couple of guns and wanted to dual wield some "primary" weapons. I had a sawn-off izh43 on my back and took a Blaze 95Double Rifle in my hands. I then started eating something (tested with multiple types of food). After eating I picked up the gun again, but it was still in my vicinity tab. It wasn't visible on the ground though. I told my friend what happened and that he should try to pick it up, which worked. (Wasn't visible for him as well) We both had a gun on our backs and the Blaze in our hands.
What happened next creeped us out a bit, he ejected the ammo out of his blaze, which happened to mine at the same time. He then reloaded it, which happened to mine too. When reloaded and shot, both of our guns emptied.

My conclusion: We had twin guns? Everything done to one of our guns happened to the other.