All those 3D-printable guns recently seem to be cheating, using nails and brass cartridges and such. Also, they appear quite dangerous to use.
This inherently safe design remedies those drawbacks. The gun and ammunition are made entirely from printed parts, plus a few short pieces of 3mm filament.
Fundamentally, it's a multi-shot, semi-automatic design with a smooth barrel and hardly any recoil.
A few aspects of the design are parametrisable, including magazine capacity, barrel length and caliber.
The default parameters in the OpenSCAD file are tuned for PLA. In tests, muzzle velocities up to 40Km/h have been achieved.