Google translate of archive.org snapshot https://translate.google.com/translate?hl=en&sl=pl&tl=en&u=h...
Deep space mission is send to a distant solar system where signals of intelligent civilization have been discovered. As they approach the planet all the signs, radio waves, artificial lights, etc progressively disappear. Meanwhile on the planet we are introduced to the society which solved all of the world problems by providing everyone with a job, all thanks to invention of a timed catalyst able to disintegrate any matter after coded period. Every item on the planet is programmed to turn into dust on expiry date, "durability of single-family houses - up to 15 years; passenger cars and their parts and accessories - up to 1 year; TV sets and radios - up to 1 year; clothing and footwear - up to 6 months; underwear - up to 3 months.", perfect planned obsolescence on a global scale. Unfortunately there is an accident at one of the catalyst producing plants at the time of deep space mission approach. Giant spill creates chain reaction eating everything on its way. Narrator goes back to the space mission, now landing on a barren planet, with astronauts embarking and looking around confused at the sight of an empty world.
You can print a plastic device, insert one nail (needed for a firing pin), and fire bullets that can kill a person.
Is it accurate? No. Durable? No. A crappy gun? Definitely!
But I think that this meets most people's idea of a meaningful concept of a gun. A weapon with a barrel and a trigger. Pull the trigger, there is a bang, and a high speed projectile goes where you pointed it at.
The design that I was talking about was 2013. Since then there have been legal issues back and forth. Entirely plastic designs probably exist, but are not legally available.
I could use a 3D printer to create a solid block of plastic and then hand carve it into a doll. But, nobody would call the doll 3D printed even if one of the steps was 3D printed.
Also, I don’t think a gun needs a firing pin. You could have a gun where the trigger release a spring that brings two chemicals together that react violently, thus firing the bullet.
It had 2 metal parts. The first was a nail for a firing pin. And the second was a useless hunk of metal whose only purpose is to make metal detectors go off. (Thereby avoiding being illegal because it is concealable.)
Fabrication with preinstalled thermite charges would generally suffice. You'd know there had been a device there, but it would be difficult to reverse-engineer.
It beats beating on stuff with axes:
Sensitive electronics are small-batch (if not one-off) deployments. Mixing volatiles and circuits with confinement and altitude tends to put a lot of risk adjacent to extremely low tolerances for out-of-range behaviours.
At the very least, that's an argument for using a Standard Thermite Pack separately packaged (and possibly with separated incredients and factors) which could be applied as needed, when needed.
Or some equivalent mechanism.
I’m not a chemist, but reading https://en.wikipedia.org/wiki/Phthalaldehyde#Disinfection makes me concerned a bit, as “disinfectant” often means “kills stuff”.
Materials scientist and polymer scientists here:
Just because it depolymerizes doesn't mean it does so into happy stuff. Photodegradation is the process of degrading with the application of photons (typically in the visible to UV range). Many things, especially plastic things, degrade in the sunlight, some faster than others. But then, when it degrades, when those monomers (single repeat used to make a polymer) split up, what did you just release into the environment?
If you want to understand this process more, here's a good and accessible read: [Photodegradation and photostabilization of polymers, especially polystyrene: review](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4320144/)