I downloaded a bunch of files for printing the “liberator” etc... and also for CNC made “ghost gun” receivers a long time ago. But then when a friend wanted them... I could not figure out where I saved them.
Finshing an 80% receiver for a “ghost gun” is a worthwhile project. There really is no need for a CNC machine to do it. And the 3-D printed guns are basically a waste of time. The goal of the project was not to make a worthwhile firearm. It would take hours to complete. And if you print one up without inserting metal into it... you have created an illegal firearm that could get you into trouble. You can put together a homemade “zip gun” from hardware store parts in a few minutes that is more durable and safer for the operator.
Strictly for fun I once assembled a slamfire shotgun using a couple lengths of pipe and a roofing nail and some other bits and bobs. Wouldn’t want to take it duck hunting, but it worked reasonably well enough for a few bucks worth of raw materials. Good knowledge to have in case I ever get cornered at a hardware store with nothing but a single shotshell in my pocket.