I have a MSAR (Microtech Small Arms Research) STG556. It is a clone of the Steyr AUG that was produced for a short time by the knife company Microtech. It is chambered in 5.56 and uses proprietary mags out modified AUG magazines. I have two 30 round MSAR magazines and three modified Magpul AUG magazines. 
the previous owner had a trigger job done on this one and it has the nicest bullpup trigger I have ever felt.

 It has A Vortex 1-8x LPVO in an Atibal cantilever mount.