M13B UNLOCKED

 There are a few ways to unlock the m13b. 
 You will find it in the  radiation zone in warfare 2.0 DMZ you will find the guy wearing a yellow suit. He is called the chemist.  If you go in on foot, it’s best to have someone with you. He is heavily armored and he will fight back and there’s a lot of AI surrounding him also firing at you if you want to go in solo the best way is to bring a vehicle and drive around and run him over and all the AI bots with him jump out quickly grab the gun and run off, you will need to extract to keep the gun. Be careful as other players are also going for the chemist, and they will also camp at the extraction point the tip : I would suggest is go to the extraction point that closest but not the closest extraction point, extraction point is often often being camped at.