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).
For long-range shooting in the field, a good bipod is a must. This Harris model adjusts from 6 to 9 inches high and is ideal for working from prone. With the Black Hills 175-grain Match hollow-point load, this rifle shoots astoundingly well; just as well as the four-grand custom rifle.