We’ll get to the upgrading part down below. You’ll be able to purchase them from Pack-A-Punch machines in the mode, getting them at whatever Tier you’ve upgraded them to. How to Get Ammo Mods in Black Ops Cold War Zombies Each bullet has a change to explode dealing additional explosive damage and destroying any impacted armor. Shatter Blast – Bullets deal explosive damage.Brain Rot – Makes a zombie attack other zombies as part of your squad.Napalm Blast – Deals fire damage to enemies.They essentially add effects to the rounds you’re using that burn, freeze or stun the zombies you’re fighting to avoid. What they are in the game is a Field Upgrade that you can purchase. If they’re confusing you a little, here’s everything you need to know about how to get ammo mods in Black Ops Cold War Zombies, how to upgrade them, and what they do. One of the most interesting is ammo mods. While most of the fun in Black Ops Cold War‘s Zombies mode comes from simply blasting the undead away, it’s a complex mode full of secrets to uncover and upgrades to unlock.