The chest rig or chest rack, really gained its fame during the Vietnam War. The canvas rigs dominated the NVA inventory for carrying AK-47 magazines throughout the war. Many US Special Operations Forces stole or copied the design to better blend in & use enemy weapons.But, the truth is that military carrying equipment on the chest has a been around for a very long time.
Chest rigs are a great option for carrying gear as long as you keep the load out focused on quick need items. I prefer to think of chest rigs as a place to store rifle magazines, communication devices, and navigation gear. The chest rig is another tool to assist with economy of motion in accessing gear needed in a hurry and is a compliment to other equipment like a battle belt. A chest rig is a supplement and not a replacement for other kit.
Chest Rig Pros
Energy Conservation: weight carried higher on your torso is more efficient when traveling over level ground. However, this isn't true when traveling on slopes and steep grades.
Quick Access: All your equipment is right in front of you. If organized well, there is no need to dig around or hint for gear. Due to the high profile, you will have access to your gear while crouching and kneeling.
Vehicle Entry/Dismount: Due to the lack of gear on your back, getting in and out of vehicles is more convenient. You are able to sit in chairs and against trees more readily. The excessive use of vehicles during the Global War on Terrorism, caused a reimagining of chest rigs with MOLLE systems.
Chest Rig Cons
Hold Heat In: Chest rigs hold heat in during movement and can potentially cause you to overheat in warmer climates.
Going Prone: Wearing a chest rig, even if it is a low profile or minimalist style prevents you from getting into a full prone position. Chest rigs also increase the profile of your silhouette, which makes it difficult to get maximum use of cover and concealment.