- play with at least 2 other friends
- everyone picks 2 orbital stratagems with "barrage" in the name
- decide on a ditch where to throw them
- everyone readies the first one, count to three, throw at the same time
- everyone immediately calls the second barrage stratagem and throws them to the first one
They don't need to be in the exact same spot but in close vicinity. If you are 4 players the chance is higher to get it. Every player that is present when the stratagems are enough gets the achievement.