I had figured they were all using AK's???
No. The Greek and Armenian middle men running the arms business have a vast assortment of whatever falls off the back of a truck in Europe.
By the color scheme, that is a Stg77, aka AUG. Stolen from Austrian military or a contract gun for Argentina, Ecuador, Oman, Saudi Arabia, etc.
Lots of guns floating around out there on the grey market.
Your homework assignment: watch Lord of War and report back.