It could be found in Wooden storage crates, Green storage crates and Blue storage crates.
It could also be crafted assuming the player had correct material to do so. It is unknown whether 556 Ammo was a default crafting recipe.
A 556 round could be crafted with:
It took 0.3 seconds to craft a single bullet.
- The 556's full name is the 5.56x45mm NATO.