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).
According to the U.S. Army, the average soldier will hit a man-sized target 10 percent of the time at 300 meters using the M16A2 rifle. 1  Graduates of the U.S. Army sniper school are expected to achieve 90 percent first-round hits at 600 meters, using the M24 Sniper Weapon System (SWS).