Can I build my own firearm without a lisence? Can it be automatic?
Well, you'll know for sure, after the court case verdict is read...
Here's what you're looking at.. prior to the AR becoming everyone's DIY project, there were (and still are) a small number of custom rifle builders in the country. And I don't mean guys taking an action and building a custom sporter from a milsurp, I mean guys who built it all from scratch. High end bolt guns, generally.
These guys were building maybe a dozen rifles a year, usually less, and because of the low numbers made, were not required to have the Fed license to manufacture firearms, like the big arms makers. This was what the law had to deal with for many, many years.
The key is the govt's interpretation of "engaged in the business" of dealing in firearms. Very small numbers of guns made, and sold were traditionally considered exempt, not worth prosecuting. That was then.
A future administration can change their minds, anytime they want.
Making a gun, for your own personal use is, as far as I know legal without any license or permits from the Federal govt. Check you state and local laws, which may differ.
The gun has to be of a type that is legal. SO, no full auto (or other NFA regulated weapons without prior govt approval).
There are some grey areas, about selling guns you made yourself, when you get tired of them, etc., because you are then dealing with business & commerce laws.
Also remember that an honest difference of opinion with the Govt can land you in court. Also the govt doesn't have to worry about expenses taking you to court. Their costs come out of all our pockets. Your expenses come out of your pocket alone.
Might just be urban legends, I can't give you any cites, but I have heard of two cases where the govt took people to court over "Thompson submachine guns" they made at home.
The first one was a complete faithful repro tommy gun, correct in all dimensions, including barrel chamber and rifling. It was capable of chambering live ammunition. And, except for springs, was made entirely of wood.
The second was a faithful reproduction of a Tommygun, all parts workable, but scaled down. The gun was about 4 or 5 inches long. A scale model, in steel and wood.
Govt said they were illegal (unregistered & untaxed) machineguns.
They lost both cases. (no conviction) but it was still expensive for the owners.
Any guesses why the Govt lost???