Dumb question here, I was under the assumption that you can make the 3D printed parts, but you still need steel for parts like the barrel and springs. I also thought that 3D printed guns don’t have the life of a steel gun?
The 3D printed parts are the frame and hand grip. The barrel, firing pin, and all springs must be steel. The printed parts will eventually deform or break, or just melt if the barrel get too hot. Trigger group parts can be 3D printed, those having a very short life. Most people put purchased trigger parts into the lower housing.
The electro-chemical machining for the rifling is very rough and crude. That limits the range and accuracy. The barrel must be machines on a metal lathe. One must either make or buy a chamber reamer.
Those weapons do shoot, and sometimes will work for a few weeks. They certainly can be used in the process of gathering well manufactured weapons from the battlefield.
The FGC-9 is a hybrid design which uses a steel barrel, bolt and springs.
The design was meant to be made with a minimal investment in tools, using widely available steel and springs. One of it’s major innovations was the homemade, relatively high quality steel barrel. It uses the strengths of both 3D printing and commonly available steel items to produce a firearm approaching the longevity, accuracy and reliability of low end factory produced firearms.
This dude’s design required like a trip to the hardware store for a pipe to use as a barrel, and springs and other stuff to serve as the metal parts. The plastic was designed to keep it all together, and not wear on itself.