@contrex,
The prototype the first of it kind is just that IE a proof of principles and little else however better such weapons will be design in short order.
Next it is not mainly the US that "need" such an at home printed/manufacture weapon/firearm but citizens of nations such as the UK/China/Japan with almost a complete ban on firearms.
Desire a firearm for protection going to the ATM download the plans from the cloud and then print one out in a few minutes for a few dollars and then destroy it after getting home along with wiping the plans off your computer.
When there is a knocked on your door looking for illegal weapons the reply can be what illegal weapons as I would never never assume the right of self defense.
As I said before game over as far as the ability of governments to disarmed it citizens.