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).
Ranging capabilities for reflective targets extends out to 1000 yards, for hard objects (such as trees) 650 yards and for soft targets (animals) the max distance is 325 yards. Bushnell has certified the unit to be fully waterproof sealed with O-rings and charged with nitrogen to avoid any internal fogging on the lens.