Why not right?

Printed in PLA with a bullet weight of 13 gr.  It’s really too bad that a heavier plastic doesn’t exist… 13 gr is very light.

From the video description:

A total of 14 3D printed 9mm bullets were fired without any problems.  The bullets loaded with 1 grain of powder were subsonic and showed good accuracy potential.  The bullets loaded with 3.8 grains of powder went supersonic, but we did not test accuracy.  The recovered bullets show evidence of engaging the rifling.  The bullets also seem to have frangible properties, as they disintegrated when the impact was hard enough.

It’s cool people are experimenting with stuff like this.  I can’t wait to see where we’ll be in 5 to 10 years.