Guns

It’s not really hard. I have tested 3d printed 9mm rounds with a 209 primer and it shoots with out black powder

If you use caliper and get the exact measurements and have it access to a 3-D printer, you can duplicate it pretty well you might have to modify it a little bit

The recipe for smokeless powder is a closely guarded secret, although it can be found if you know the "right" people. Even if you know it, producing it for yourself is a highly risky endeavor. Assuming you can produce the cases, powder, and bullets, you then have to produce the primers. Primers have a high explosive compound that is incredibly volatile when finished, but the raw ingredients are also dangerous by themselves.

At the end of the day, the "survivalists" as you call them, are right to acquire all of the pre-made parts themselves, and assemble ammunition as they need it. In a SHTF scenario, perhaps a decade in, people will most likely resort to black powder loads, which will work, but with drastically reduced performance and reliability.

There is an alternative to black powder and it’s called white powder (sugar rocket powder). It’s just powdered sugar and potassium nitrate, but you have to grind it up yourself because the store bought stuff has cornstarch in it. You can get potassium nitrate as stump remover or you could go the old-fashioned Way in take it from stale urine but that’s disgusting.

What 3D printing material is used? I guess the material is expensive to withstand such high pressure and temperature. It is estimated that it cannot be recycled after use because the gunpowder is likely to have been integrated into the printing material. If the gun is fired continuously, the high temperature in the barrel is likely to stick the shell in the chamber.

I have seen some inferior 3D printed firearms in Southeast Asia. Some of them cannot even finish a whole magazine, and the printed parts where the barrel contacts have begun to melt and break.

3D printing materials can only be used as a supplementary means of emergency，Conventional ammunition still has to use brass or steel, and aluminum alloys may also be used as an alternative for low-power pistol bullets.

There is no way to solve the problem of black powder residue after shooting even in modern times. If you don’t want to perform maintenance after shooting 10 rounds of ammunition, you can only solve the problem of making nitrocellulose, or make some cheap disposable firearms with short lifespans.

I use pet filament recycled from soda bottles. so far I can get the 5 fires out of one shell before it breaks. I also make white powder. powdered sugar with potassium nitrate and it seems to fire faster and cleaner and so far I haven’t had any issues

nope, you can read the urbanski 《Chemistry and Technology of Explosives Vol .3》，you can found the smokeless powders production process and recipe

did you read the 《Ammunition Making-NRA》？

https://ia904700.us.archive.org/21/items/AmmunitionMakingNRAByG.Frost1990/Ammunition%20Making-NRA%20%20by%20G.%20Frost-%281990%29%20_text.pdf

that link won't work, try this one, download the PDF file version or full text version:

https://archive.org/details/AmmunitionMakingNRAByG.Frost1990