The Ammo Mod upgrade is a system introduced in Call of Duty: Black Ops Cold War, functioning as an evolution of the Upgrade Modules from Call of Duty: Black Ops III and the Alternate Ammo Types from Call of Duty: Black Ops 4. Ammo Mods can be added to any standard weapon either via the Pack-a-Punch Machine for 2,000 Essence or via finding an Ammo Mod pickup earnt from a source, such as a World Event in Outbreak. Unlike the prior games, the weapon does not need to be Pack-a-Punch'ed to be equipped with an Ammo Mod.
They are also one of the items that can be upgraded with Aetherium Crystals to enhance the power of them, with five tiers of upgrades being available.
Specific Microtransactional blueprints is noted to come with "Elemental Damage", these blueprints come with a weakened version of the related Ammo Mod tied to said element, only dealing additional bonus damage upon matching elemental weakness of an enemy. These blueprints are also "Elementally Locked", in a similar fashion to Wonder Weapons, and can only receive the matching Ammo Mod tied to the element that it has.