"Warzone 2" launched today at the same time as the "Season 1" update for "Modern Warfare 2". The two games share many similarities: weapon pools, progression systems, and battle path progression are all synchronized between the two games. Traditionally, playing either regular multiplayer or Warzone would unlock everything, but one of the new weapons in Season 1 is locked behind a Warzone-only challenge.

The M13B, an assault rifle that Infinity Ward touts for its high rate of fire and low recoil (two stats required of CoD guns), is the only new gun in today's update that cannot be unlocked simply by advancing through Battle Pass.

The requirement to unlock the M13B is instead to jump into Warzone 2's new sandbox escape mode, DMZ.

The challenge description for the M13B assault rifle is as follows:

"Unlock it by defeating a chemist in the radiation zone of the DMZ and retrieving his dropped weapon."

I believe this is the first time in Call of Duty history that a gun is locked behind a PvE boss fight. The chemist is in the radiation zone of Al Mazrah, but only if you are playing DMZ, not Battle Royale. This zone is marked in yellow on the TAC map:

A few things to remember to complete this challenge:

The chemist's exact location is not marked on the map, but he can be identified by his yellow protective suit. He himself is heavily armored, with a mountain of armored goons covering him. Once killed, he can pick up his M13B. Chemist has a special M13B blueprint with pre-attached attachments.

If you want to see Kemist fight for yourself, YouTuber Geeky Pastimes' (open in new tab) brief video guide is helpful:

Extracting with this gun will not unlock the blueprint permanently (although it will remain in DMZ inventory as a contraband). ), but it does unlock the M13B for use in battle royale and multiplayer. The only major drawback is that you have to go to the DMZ several times to unlock the M13B for the whole squad.

The good news is that you may not have to kill the chemist three times. Since you only need to have the gun at the end of the match, you could drop the chemist's M13B that your friend won in the previous match, pick it up and take it out yourself, and get the unlock. Or you could hunt down a rival player who has already beaten the chemist and take the M13B from them.

As for Modern Warfare 2 players who want to stick to the regular 6v6 multiplayer, there is currently no way to unlock the M13B. This may change in the future, but this appears to be a deliberate choice by Activision to promote the launch of Warzone 2. The other two guns added today, the BAS-P SMG and the Victus XMR sniper rifle, can be unlocked with the Warzone 2 Battle Pass (opens in new tab).