Continuing in the vein of my fascination with 3D-printed firearms, Jay at Stuck in Massachusetts points to a Thingiverse post in which a gentleman shares a printed AR-15 magazine follower:
I am implementing anti-tilt functions that will be in the next revision, plus a few other changes to make it "beefy" and a magazine spring catch. The current one feeds and functions well, I put 100 rounds down range with it, no jams.... YET. Also in the works, is a whole printable magazine and spring.
One step closer. I don't know how he'll print a spring, but a commenter has suggested printing a mandrel for winding the custom spring. Another suggested that if the current state of the art can't handle printing an entire magazine, it can handle printing a mold for casting the mag in a more resilient plastic.
It's going to be a long time before we'll be able to print ARs in our garages. We'll have new firearms designs specifically made to work with the strengths and weaknesses of 3D printers sooner, but we're still a ways off from anything you'd trust to be as reliable as a factory gun in an emergency. But we're right around the corner from home-printed guns good enough to satisfy the hobbyist and the criminal. The fiction of gun control as criminal-access control is going to crash and burn in the public consciousness. Very soon, while you'll still see plenty of ideological support for gun control in the states and countries where that ideology is strongest, reasonable people everywhere will instinctively consider gun control no more effective in keeping guns away from criminals than copyright laws are in keeping mp3s away from "pirates".