A Concussion Grenade can give you the opening you need in Call of Duty: Modern Warfare 4, especially when an opponent is settled behind an objective or watching a doorway. The supplied overview lists its unlock at Player Level 15, while CoD MW4 Boosting is an option players may consider for progression.What does the Concussion Grenade do in Call of Duty: Modern Warfare 4The Concussion Grenade...