Subcutaneous emphysema is often found in car accident victims because of the force of the crash. Chest trauma, a major cause of subcutaneous emphysema, can cause air to enter the skin of the chest wall from the neck or lung. When the pleural membranes are punctured, as occurs in penetrating trauma of the chest, air may travel from the lung to the muscles and subcutaneous tissue of the chest wall.
Both the Army and the Marine Corps teach that the maximum effective range of the M16A2/A3/A4 is 500 meters on a point target (individual enemy) and 800 meters on an area target (i.e. troops in the open).
The target must travel a minimum of 48 yards, no more than 52, and it must rise between 6 and 12 feet 10 yards in front of the house. Tournament shooters are handicapped according to their average and must compete at varying distances from 16 to 27 yards behind the house.