We have begun our third generation of gun builds, the .300 Blackout SBR.
The .300 Blackout is a modification of the 300 Whisper. It is designed, principally by Advanced Armament Corporation to replace the 9mm subgun, known as the MP5SD. The 300 BLK caliber features the kinetic energy of a 7.62×39 (AK caliber), but from a 9 inch barrel. Accuracy beyond 200 yards, but in a compact system. Further advantages of the system include the full AR platform adaptability. The 300 BLK uses the same bolt, bolt carrier, upper receiver, lower receiver and all associated parts with the exception of the barrel (which is a .30 caliber). This compact system lends itself well to a suppressed platform with an overall length of less than 30 inches.
More information available at 300aacblackout.com and here http://en.wikipedia.org/wiki/300_AAC_Blackout_(7.62%C3%9735mm) .