Image by Michael Crumbling The latest 3D printed hybrid uses an old but useful concept: pre-loaded interchangeable chambers/barrels/cartridges. The cartridge itself has sufficient strength to contain the pressures necessary for propelling a projectile, and is sufficiently long enough to result in a velocity that is useful. Michael Crumling has created a relatively small round, the .314 Atlas, to demonstrate the concept as used with a 3D printed mechanism. Here is a video link showing his system being fired: Link to video at Wired The extractor groove is likely included to make priming the cartridges easy. I have thought of...