SMG - 5.56x45mm NATO - USA - 900 RPM - The Colt Commando is the shortest format of the Colt CAR15.  The early Vietnam-era versions, the XM177 and GAU-5, displayed excessive blast/flash and recurrent reliability problems.  The current versions have cured the reliability issues, but blast/flash are the price you pay for extreme compactness.  D.E. Watters 