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).
A difficult question to answer, but the average sniper rifle in the  .300-.308 caliber can shoot anywhere between 100 and 800 yards. A  .50 caliber is estimated to effective â¦ at about 4 kilometers (2.5  miles).   US snipers are trained to engage targets at ranges up to 1000  meters.