FNH had their elusive SCAR PDW on display at SHOT Show 2015.
The PDW is based off of a SCAR 16S. However the upper receiver is slightly different. SCAR uppers usually have three holes at the front behind the sling loop. That is not the case here. As you can see there are no holes and the sling loop is not at the end of the rail but about 1 inch back from the front of the upper. The folding sights are a completely different design. Stock SCAR front sights are integrated into the gas system but the PDW has a rail mounted front sight. The rear sight is also a different design. The BDC is usually a knob but as you can see, in the following pictures below, it is more like a selector lever. The handguard is flared at the front acting like a handstop. This one is 3D printed. It has internal rail mounts that slide over both side and bottom rails.
You can see the BDC lever as well as the polymer/rubber cheek pad. Underneath the pad is the stock release paddle. Similar to a HK MP5 you push the side of the paddle with your firing hand thumb and the stock and slide is unlocked. There are only three positions to the stock. Closed, middle, and fully extended.
Just for curiosity sake I tested the Alpha Jacket to see if the SCAR PDW could fit.