Grave Robber is a trait in Destiny 2 that can appear on 121 weapons. An enhanced version exists on crafted and some newer weapons.
What Grave Robber does
Melee final blows or dealing damage with a charged melee reloads this weapon's magazine from reserves.
Enhanced version
Melee final blows or dealing damage with a charged melee reloads this weapon's magazine from reserves. Improves handling.