Start a
Farm Survival game by going to Zombies > Green Run > Farm > Survival
Survive as long as you can in order to build points. Round 1 should be 5 shots to the leg and 1 stab to maximize points on killing zombies. Round 2 is 7 shots 1 stab etc.
Hit the random box as many times as possible until you receive the EMP device (looks like a flashbang).
If you do not have the device by round 10 a restart is advised or purchasing juggernog in order to minimise the difficulty of this achievement.
When you have the device simply horde up a sufficient amount of zombies (10 or more) by running in circles [around the truck in the middle of the map] and herding them together whilst avoiding being hit.
Throw your EMP device at them by pressing left bumper.
Easy 5Gs
Happy hunting
coreymawf
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All credit for this youtube video demo goes to Rooster Teeth.