5.56mm NATO Cartridge 5.56mm NATO Cartridge is an item. Ammunition. Used by: M16, M4A1, HK416, SIG516, G36C, M249.CraftingMade at Ammunition Fabricator20CCopper Ingot×3GGunpowder×2NIron Nugget×1RRedstone×1Used inG36C BarrelHK416 BarrelM16 BarrelM249 SAW BarrelM4A1 BarrelSIG516 Barrel