From The Federalist:

For $3, you can buy Karl Marx’s “Communist Manifesto,” a book that indirectly led to the deaths of upwards of 100 million people worldwide. You can also purchase a copy of the “U.S. Army Improvised Munitions Handbook,” which promises “step-by-step instructions on how to assemble weapons and explosives from common and readily available materials.” Amazon sells hundreds of books teaching readers how to build guns (and the website even sells many of the tools necessary to do it).

Seeing this precedent, I uploaded a 3D printable gun file to Amazon … as a book.