I was thinking the 030 is considered an SBS without any muzzle attachment like the one shown on reddragunweapons.
The 12K and 030 are both 430mm barrels. That equals 16.93". According to this pic of them side by side, I bet you need the muzzle attachment to get over 18". http://img216.imageshack.us/img216/2474/saiga12sisp3003oq5.jpg