First, have all the teleporters activated and the Pack A Punch machine available for usage. Get a Crawler so you have time to get in position and get the achievement. Go out of the left door from the position you spawn at or the right door if you are facing the Pack A Punch machine. Once you see the fence where the zombies can break in before the next door, slightly look through the gap to the left of the wood to see a circuit breaker in the distance. Take out your upgraded gun and shoot the breaker. This trick only works with guns upgraded in the Pack A Punch machine and by shooting the breaker. Once this is done, a sequence will begin and you will unlock the achievement.