They’re not printing the metal parts. They’re printing the frame (as in “polymer framed handgun”).

The frame is the part that gets the serial number and is considered the controlled part of the gun. Rather than the trigger, the springs, the barrel, etc.

Other than the frame, which requires an FFL for transfer, especially across state lines, the rest of the parts can be ordered and shipped from anywhere and are not controlled.

Mind, that’s changing, again notably in CA, as they now talk about “gun pre-cursor” parts.

The 3D printed frames are similar to the “80% lowers” which are aluminum blocks that are “80%” complete AR-15 lowers (the lower receiver, again, the controlled part of an AR-15).

With straight forward machining and some jigs, those chunks of metal can be finished into an operational lower receiver, and the rest of the rifle can be assembled from disparate parts ordered from anywhere.

The original “ghost gun” before 3D printers enabled folks to assemble Glocks in their garage.

It is fearmongering. You technically can print an all-plastic firearm that works for a round or so until they explode, but only after you have already printed and tested and refined multiple times over, and best case it is still an inferior material to metal. I would put it in the same category as "Yeah you can turn a tree trunk into a cannon, tell me when not to come over when you use it." You can probably make a similarly reliable firearm out of fired clay if you put in the same effort.

Some parts in regular firearms can be printed in plastic, guns with polymer parts have existed since polymers existed, but it is only marginally simpler than machining it out of metal. After all you can buy a metal CNC machine for handful of bucks more than a 3d printer and you don't have to worry about shitty materials breaking immediately.

And there are already plenty of examples of hardware store pipe guns that if someone spent more than a day or two working on it would by far surpass anything anyone can print.

People normally don't make guns that are entirely 3d printed. Homemade guns often get the parts exposed to highest stresses commercially.

Fwiw, when I paid attention to my local police department's released body cam vids, maybe around 1/3 of the guns they showed as evidence were polymer80s (edit: which I mistakenly assumed were 3d printed, but it turns out they aren't so feel free to disregard that fun fact)

In the US I believe there's many metal 'spare parts' for guns available, including the barrel, so don't need to print the whole thing. So they're usually not talking about entirely printed guns.

A pure plastic gun seems more likely to blow the users hand off than hit their target. Especially if just downloaded and printed in PLA on default settings (few walls, sparse infill...)

I know very little about guns but know 3d printing quite well. My understanding is that a fully 3d printed gun is not reliable, you need to acquire actual gun parts for the path where the bullet fires (the barrel?). Then can use 3d printing for the rest

They're pretty damn reliable if you either use a hybrid model (FGC-9) where the barrel is "explosion proof pipe" from china that is then electrically machined (easy with 3d printed mandrel) to form a nice rifled barrel.

Or you just 3d print the "receiver" for something like an Ar-15, which isn't load bearing. If you use the right materials and the beefier designs it will lats hundreds to thousands of rounds. The rest of the parts can be bought through the mails unregulated.

I heard a billionaire is funding this, he’s probably afraid of the one famous instance of someone like him getting killed by one of those.