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).
500 meters for Point Targets, 600 meters for Area Targets. How do you Mechanically Zero the M4 weapon. -Adjust the front sightpost until it is flush with the housing. -Turn the elevation to the 6/3 marking is aligned with the index line. -Place the unmarked aperture, up and the 0-200 meter aperture, down. -Turn the windage knob to the 0-200 meter aperture.