"3D printed lowers and mags are real" with the current materials they can't make barrels, which is kind of the most important part. The guy even admits the materials they have right now can't handle the forces required for a barrel.

It's scary that you could print a lower and have an untraceable gun, that's the more worrisome part of the current ability of the technogy. Moving forward with new 3D printable materials making a whole gun will be possible and that's worriesome as well.

I don't understand the fascination with firearms in the US but people will always find ways to have guns now. If anything this man is starting the conversation of what malicious things will be made when 3D printing technology becomes more and more accessible. A conversation that's better had sooner then later.

This is why 3D printing is both really exciting and really scary.

You have to ask the question on what creates the desire for a rifle like this. They can say "I want a rifle, not a hunting rifle but a military grade weapon" but why, just because? These guys seem to be saying "Just because we can" but what about the /real/ users? What would their motives be that they'd go so far? This is where things go gray and twisted, this is where it all feels wrong.

What do you mean "real" users?
Motives for creating a military-esque weapon could be attainability. Most of the new military rifles dont have civilian counterparts yet or wont have them at all not to mention the expense. There are guns that aren't made anymore or guns that never went into mass production. There's also the trouble of export imports. Certain weapons produced by certain countries can't be imported and reasons for that vary but are mostly political.

For the question of why do you want these weapons?
Why do art enthusiasts collect art? Why do avid gamers collect games and consoles?
They do it because they're interested in guns and enjoy collecting and firing them. Its a hobby that has been demonized because it easy to do so. One asshole kills a bunch of people - suddenly every gunowner/enthusiast is secretly crazy and wants to shoot up a mall. And that sounds ridiculous, but its become a deep rooted fear in society that it causes most people to scoff or become concerned when it takes the spotlight again - "Guns are bad, so the people who own them are bad and want to hurt us."

I can see what you mean by collecting guns but art and games aren't really tools or weapons (in the physical sense). When I say real users I mean those who don't get into craftsmanship or curating but for whatever other reason.

As noted in the documentary it's definitely not just "one asshole" and many hearts and lives were wrecked for each shooting, sometimes even whole communities or sending shock through a country. I do have friends who hunt for sport and own guns but definitely none like these. It's not exactly that I don't like guns at all but the guns that are too powerful concern me. Not to mention the effort that these guys are taking to make an "untraceable guns" and alternative materials meaning they don't want to be easily responsible for whatever happens or when it's in areas people specifically do not want guns like airports.

If I went to a museum and saw a historical gun on the wall it wouldn't really fase me but when someone can keep a gun that can shoot 600 rounds without failure I'd become uncomfortable, what reason would someone need to blow 600 rounds? things like that make me consider a gun to be too powerful.

The thing is people consider other hobbies different when really the reasons behind them arent.
Someone wants a big original Picasso. Why? Because they like it.
Someone wants a big military rifle. Why? Because they like it.

You try to put reason behind a hobby and they all become pointless. Throw in some controversy and now its something you can be concerned about. Fear is a pretty big factor as to 'why' guns should and shouldn't be ____ and its not unfounded, but it is a little excessive. The majority of gun owners are responsible, well-mannered people like you and I. Most people who want big military rifles are like you and I, their interest just happens to be in fire arms.
The answer to your question of why does someone need a 600rpm military rifle is simple. They dont - but its not about necessity and it never was. They want it probably because they find it wicked fcking awesome.
Its like asking someone why they need an expensive sports car. They don't - but its wicked fcking awesome and they want it.

As for making it untraceable that comes down to individual beliefs - most people dont want their guns taken away if for some reason martial law is declared. Also lets remember what we're talking about - how would these be traceable if you could just print them out and why would you go through the hassle of registering them when you could just print another? The materials question is answered here to - you're not going to get a real steel weapon from 3D printer. Alternative materials can just be a case of cost or weapon weight/durability/survivability etc etc. that all is effected by what the gun is made of. You should automatically assume because someone was a carbon composite weapon that happens to not be detectable by metal detectors that they're trying to make themselves less of a suspect.

P.S. I hate suffixes and they hate me.