The Liberator "pistol" fired a .380 ACP round which has been shown to be a decent self defense round.
The Grizzly "rifle" fires a 22LR round which is useless in self defense situations.
Regardless of it's external shape, this is probably a regression in development of 3D printed firearms. Especially considering the load pressures, both the 380 ACP and the 22 LR are around 20,000 PSI to 25,000 PSI.
A real rifle round? Well your looking at anywhere from 50,000 PSI (such as the 7.62x51mm NATO aka M14/M24/SR-25 etc) to 62,000 PSI (such as the 5.56x45mm NATO, aka AR-15's/M-16's etc)..
Till they develop a plastic that can handle those stresses and be 3D printable, the most anyone will be able to do rifle wise, is to make a carbine using a pistol caliber. Although some pistol rounds such as the 9mm Parabellum (most common 9mm Pistol ammunition) is 39,000 PSI which will probably push any 3D printed material well beyond it's maximum.