It's not yet ready for prime-time (it has yet to be tested), but 3D printing tinkerers have developed a design for a semiautomatic pistol. In fact, the developer says a full-automatic version would be easier to make with available materials. What a long way we've come, in just a few short months, toward the ultimate goal of rendering gun control laws a complete joke. Well...they were already a joke (though a dangerous one). It's more accurate to say we've come a long way toward rendering such laws moot, and easily bypassed by even those with limited technical skills.
Over at DEFCAD, Proteus, a moderator and developer of the design (which another poster dubs "the brick" for obvious reasons) writes:
I have designed a .22 LR Semiautomatic firearm. Unlike former designs such as the Shuty, this design uses almost all plastic parts (All non-plastic parts currently except the FCG cannot physically be plastic or a semiautomatic will not function) and uses weights to bring the bolt to a correct weight. You will need the following parts:
*3D Printer with ABS capability
*AR-15 Buffer Spring
*Ruger 10/22 Mag Spring
*AR-15 Firing Pin
*1x8mm metal insert (Case extraction)
*.44 bullets to weigh down bolt (More info in the .readme)
The barrel uses an insert around the case, but then the rest of it has a plastic bore, which means it is pre-rifled and therefore complies with the ATF.
Magazines available in 10 and 30 round versions. NOTE, although they are based off of 10/22 magazines, they MUST be printed as they contain a built in mag-catch and will NOT work in a 10/22 rifle.
Strictly speaking the design isn't completely printed, since it borrows its fire control group from an AR-15. It also uses a nail as a firing pin, as do most 3D-printed guns.* As of yet, printing the relatively delicate working innards of a semiautomatic firearm on a printer isn't quite practical. That may change with a refined design, or when patents on selective laser sintering expire next year, bringing about an expected drop in the cost of 3D-printing detailed objects, including those made of metal.
Separately, Proteus writes, "Fully automatic would actually be EASIER than a semiautomatic to design (open bolt). However... I do not want to do this at this time because of the legal implications. But Fully automatic would be simple to create, including a printed custom FCG." As you might guess from an open forum like the one at DEFCAD, participants take pains to keep their efforts legal within the jurisdictions where they live.
What goes on in quieter developments, elsewhere, is anybody's guess. But if thinking about it makes the control freaks sweat just a little more, so much the better.
*Actually, it uses an AR-15 firing pin. I confused this point with a post discussing using a nail in a different design.
Update: Proteus asked me to clarify that DefCad is the search function, while FOSSCAD (Free Open Source Software & Computer-Aided Design) is the design community working on these innovations. Designs for "The Brick" are now available here.