The M13B is the new assault rifle that launched with season 1 of Modern Warfare 2. Unlike the two other weapons in MW2, this weapon needs to be unlocked by playing the brand new game mode, DMZ. Here, you’re tasked with going into the new warzone map under the DMZ mode, and then fighting AI, looting and then extracting your gear.
How to unlock the M13B in DMZ
You will need to beat the Chemist to unlock the M13B in MW2, Wazone, or DMZ. The Chemist is a boss AI found in randomly spawned in the radiation zone, which is marked with the radiation symbol on the map. Players will need to head over to that direction of the map. On your way,m you will also need to loot Radiation Blockers. You can get these items from medical stashes found in buildings through the game map. If you go into the radiation zone without consuming them, you will be caught and start taking damage slowly over time.
Once you’re inside the radiation zone, you will need to fight plenty of hostiles in the radiation zone. Be aware that when you approach the location, a message will appear on your screen that says the Chemist is nearby, this will broadcast to the other players, similar to how enemy squads foing stronghold is broadcasted across the map.
Eventually, you’ll stumble upon an enemy called the Chemist. Kill him, and then you can loot the M13B from the floor near the Chemist’s corpse. The chemist is the dude in the yellow jumpsuit by the way. Now, you need to extract from the DMZ by looking for one of the exfil locations on your map. Head to these locations without dying, and you will extract with the M13B. If you do that successfully, you will unlock the M13B in MW2.
This may need some trial and error, and you will also need to avoid enemy players who want to go to the zone to unlock the gun. It might be a messy fight in the early days of DMZ, so good luck unlocking the gun.