I own an SU-16C. Not sure where you live, but I would recommend the C if your state allows it. I bought mine so I could fire it with the stock folded, if necessary. Mine has been accurate enough for me. You can use 5.56 or .223 in this weapon.

I second going to the KTOG site http://www.ktog.org/cgi-bin/yabb2/YaBB.pl?board=105 to get information and questions answered. These folks have a tremendous amount of experience with the SU-16.

Good luck with your quest.