Well, you asked for it lol.

you could easily show me a source with the number of victims of 3d printed fire weapons, legally owned commercial fire weapons and illegally owned commercial fire weapons, in California or the US as a whole.

For starters, no one in the US is doing this. There is no source for the number of victims of 3D printed firearms anywhere, the best you're going to get is from the limited places where authorities are tracking the number of crimes involving "ghost guns", which could be a 3D printed firearm, a home manufactured firearm by other means, or (most commonly) a legally purchased firearm which has had the serial number removed. Everytown (puke) has some statistics claiming 208 murders or shootings linked to a ghost gun and 134 "recoveries" of ghost guns, nationally since 2013. As you can see, that's not a lot. My point is, you're right that ghost guns aren't really a big problem, but that's not because they aren't viable as firearms. I think this is a moot point anyway, there are over 400 million guns in the US and millions more every year. The cat is so far out of the bag that it returned with a litter of kittens which are also out of the bag. Trying to control gun crime in the US by limiting supply is futile, but it looks good on a political platform so it's gonna keep happening.

But that's not even really what I was commenting on. The idea that FDM printing is not viable for home manufacturing firearms is at least 10 years out of date. First, it's important to understand that in the US, the "critical" part is the one that's legally considered the firearm. Every design has a serialized part which is legally "the gun" and which you (generally) must pass a background check to obtain. Everything else to construct a firearm is available online shipped directly to your door or over the counter without any kind of background check, at least in the vast majority of states. Even in the places where that's not legal (like California has recently done), it's very easy to for anyone trying to dodge that law to do so.

As an example, one of the most commonly 3D printed firearms is a Glock. With glocks, the frame is the serialized part. It's already made of polymer. So most people 3D print a frame, generally from PLA, and buy the rest of the parts to assemble the firearm. This is what Luigi (allegedly) popped a CEO with. In his case, he also 3D printed a suppressor which rendered his gun no longer semi auto, which would happen with a factory glock too, but generally these 3D printed glocks are nearly as viable as a "real" one for at least a few thousand rounds. I'm not gonna bother linking directly to anything here because again, most commonly 3D printed gun. Put "3D printed glock" into youtube.

For a more "real" scenario, you can take a look at Myanmar, where rebel forces have been 3D printing firearms to fight the Junta directly, in combat. They've mostly used the FGC-9, which, while not 100% 3D printed, does not require any "real" firearm parts to produce. Everything you need can either be 3D printed or acquired at a hardware store. You can even produce a rifled barrel at home (PDF warning) using a 3D printed jig and ECM.These 3D printed guns have mostly been a means to acquire actual military firearms from the Junta itself, but it worked, so these guns have been successfully employed by teenagers against a state military force.

For some other examples, here is the Orca (3D printed AR-15), the Plastikov (3D printed AKM), the mac n cheese (3D printed mac 10) This one is extra fun because you can get a set of "wind chimes" to complete your build. There's also the NylAUG, a surplus AUG parts kit which can be purchased over the counter with a receiver 3D printed in Nylon. Hell, the US army 3D printed a 40MM grenade launcher nearly a decade ago, and there are DYI versions too. There are many, many more designs. I think I've made my point.