Treyarch's Zombies returns in Call of Duty, bringing a large-scale Zombies extraction mode to Modern Warfare 3. Despite not being a traditional round-based experience, many core Zombies feature return, including the iconic Pack-a-Punch machine. However, it's not exactly the same as you might remember, so here's everything you need to know to upgrade your weapons in MW3 Zombies.

How Pack-a-Punch works

MW3 Zombies is played on Warzone's brand-new Urzikstan map, and there are Pack-a-Punch icons marked on your map. These are always going to be located in each of the three threat levels on the map.

The classic Pack-a-Punch machine lets you upgrade your weapon three levels. In MW3 Zombies, you can still upgrade your weapons three times, but you can only upgrade them once per zone, meaning the low-threat zone is only good for the first weapon upgrade. You'll need to venture off into the next threat level for the second upgrade, and you'll need to battle through the high-threat zone for the third and final upgrade.