It's all about "friction"

You can Make a Bump Stock on a 3D Printer.

No, I can’t. I don’t own a 3D printer. Neither do most criminals. What you mean is that the few people who own 3D printers and have the skill to use them can print bump stocks.

Chances are, you’re not one of those people.

Again, laws are not designed to stop the most motivated super-criminals. They have lots of ways to get weapons.