It acts similarly to the Pack-a-Punch machine from Zombies, but there are a few major differences. Upgrades are permanent, meaning one can get rid of an upgraded gun and then buy it again off the wall or from the 3D Printer but without needing to start over with all the upgrades. Players to upgrade their weapons a maximum of 19 times per weapon up to Mk20. Each map has a secret experimental Upgrade Station which can be unlocked by completing the Easter Egg and will allow players to upgrade one more time (for a grand total of 20 upgrades) to Mk25. Each time the player upgrades the gun, it will replenish ammo, gain a new camouflage, and get increased stats. In specific Mk levels, a new attachment (such as a Laser Sight or Red Dot Sight) may be added or maximum ammunition may be increased. What camo a weapon gets is decided by the Mk level, and the final upgrade to Mk25 grants diamond camo.