Thanks for the highly informative post. I don’t know much about metallurgy and it’s always nice to learn from an expert.
Based on your description, I don’t see any way, for instance, to make a usable spring with the printing technique. It might be the right shape, but would it be heat treated and tempered so as to function properly? Not as I understand the process.
They’re working on ways to make springs - they have different forms (much more complicated forms, in some instances - but they can do complexity easily in 3D printing), but they perform the same functions.
The problem in gun designs is that they’re very space-limited, and the current designs want either:
a) “flat” springs, such as you find inside a S&W revolver (eg, the mainspring), or in a side-by-side shotgun, or in older external hammer percussion cap rifles/shotguns. These are very easy for a trained gunsmith to make from flat spring stock.
b) “coil” springs, which gunsmiths make by winding music wire around a mandrel.
Both require high-carbon steel that has been hardened, then tempered.
The way they’re coming at it in 3D printing is to come up with complicated geometries that they can print, which, when put into a confinement tube or restricted in some volume way, turn lower hardness materials into suitable springs.
But even if you had to make springs, it’s easy. Really. Flat springs take some skill with a file and sometimes a hammer to forge them, but coil springs? Feh. Pud easy. Probably one of the easiest parts to make on a gun.