When things get serious these could be seriously useful.
If the materials science for these object-building machines gets beyond plastics, it might be another story.
The plastics will get even better. The intake on my car is plastic.
The failure they suffered on the 5.7mm design was snapped threads on the buffer tube. May just need a redesign to take a threaded sleeve made of metal.
The press will go ape when they realize that the Feds only track the lower (what is being made here) and that anyone can mail order the upper without a background check, etc.
I haven't read extensively about these, but I wonder who put together the trigger mechanism for their prototype. There is more to it that hitting the print button and snapping the two pins for the upper in...
It would imply some kind of spring. But it might be designed to use a spring that is commonly available at hardware stores.