Iron Lungs is a tier 3 perk in Call of Duty 4: Modern Warfare, Call of Duty: World at War and Call of Duty: Modern Warfare Remastered that increases the time a player can steady a sniper rifle's scope from 4 seconds to 9 seconds. However, holding the rifle steady until the 9 second limit will cause the sniper rifle to sway uncontrollably, and will take 10 seconds before the sniper rifle can be steadied again, thus, it is reasonable to not steady the player's aim indefinably but just long enough to see a moving target. Iron Lungs is only used for sniper rifles without the ACOG Scope attachment; it will not work for any other weapon, even with the ACOG scope attachment. In Call of Duty 4: Modern Warfare and Call of Duty: Modern Warfare Remastered, the perk is unlocked at level 26. In Call of