

Only the non critical to function parts can be plastic. IE, the barrel can’t be plastic. And you can use literally anything else other than 3D printed stuff.
So why is 3D printed even an issue. Anything… A CNC, scissors, metal, a grinder, wood, springs, screws…can be made part of or be used to make anything else. Making things is not magic and a 3D printer is not magic either.
The highest pressure rated plastic has a Ts or just maybe 28ksi. But with 15% elongation and a really weak modulus. So you can make toys basically.
So if you look at a tiny blade of grass and a gigantic tree its like looking at a Chihuahua and a brachiosaurus. And there are smaller things and bigger things in the aminal kingdum!