Serbian Zastava Arms has introduced a new rifle during the “Partner 2017” International Fair of Armaments and Defense Equipment held in Belgrade, Serbia. The rifle is called MAR which stands for Modular Automatic Rifle.
It is easy to notice that this rifle is based on AK-47. However, it has some design differences and improvements. The most significant one is the possibility to quickly change the barrels. The user can change the barrels to switch the calibers from 7.62x39mm to 6.5mm Grendel and vice versa. Earlier, Serbia has adopted the 6.5 Grendel (6.5x39mm) in small scales and looks like they are considering keeping it along with the 7.62x39mm cartridge.
Although the quick change barrel system is a good feature (something that AKs always lacked), I think the Zastava engineers made too bold statements about it. I’ll just quote the ArmyRecognition.com:
According to Zastava arms engineers, this is the first assault rifle in the world which is designed with the capacity of changeable barrel.
The rifle also features telescoping and folding stocks. Note also the different style safety selectors on different models. The straight magazine is possibly the 6.5mm Grendel one because that cartridge has a minimal case body taper which should allow using those straight magazines. The rifle feeds from either 20 or 30 round magazines. I assume the straight ones are also the 20 rounders because the traditional curved AK magazine is definitely a 30 round one.
The top one-piece Picatinny rail is either removable to allow a classic AK-style disassembly or the gun has a different disassembly way.