Lt. Mike Ash Command & Control Central (MACV-SOG) test fires the Sionics SSC. This is probably the only known photo of this rare gun being seen in the wild. It looks like a rechambered and barrelled M1 carbine action but it is not.
Made by Plainfield Machine Co for Sionics, it is a 9mmx19 action that is manually operated. The suppressor is a Sionics model and only 10 of the guns were made. The optics is a 4x Tasco.