Pretty simple to replicate, all you need is two Mozambiques and the shotgun bolt in question.
Pick up one Mozambique.
Pick up the Shorgun bolt (Equip it on the mozambique).
Pick up the other Mozambique.
Drop the double mozambiques.
On the ground you will find two mozambiques and two shotgun bolts.
Could be broken, can lead to a team being fully kitted with gold shotgun bolts pretty early.