To my knowledge, one rarely sees these for sale within the aftermarket firearms venues. It's what is called a Springfield Armory SAR 4800 chambered in 5.56 / .223 Rem. Otherwise it may be referred to as an IMBEL MD-3 rifle. It takes standard AR-15 magazines.
The one pictured below that I purchased yesterday, had a 20" match grade target barrel installed in her, and the dude that I purchased her from swapped out the Springfield Armory AWB-compliant thumbhole polymer stock for the below pictured grip and stock (which happens to be U.S. and not Metric; he made them fit; they should have be