I make my own to save money and because it is fun. It is simple to do so, but I still have to pay the same $200 tax and wait months for approval of the application.
The controls/tax put on machine guns, silencers and short rifles/shotguns back in 1934 was meant to be a de-facto ban. That pesky 2nd amendment got in the way I guess. That $200 tax back in 1934 is equal to about $3500 today, so I am surprised that Congress has not tried to increase it lately.