I can understand why you are confused.
I suggest that you write a letter to BAFT and your state attorney general telling what you want to do and asking their advice. I am sure they would be interested in hearing from you.
That would also help define what kind of "banned" weapon you want to know more about.
There are weapons banned by state law and some banned by different federal laws. For example there are firearms that are "banned from manufacture and importation" by the federal government associated with the Assault Weapons Ban that will soon sunset.
However, that bill doesn't "ban" the ownership of such firearms if they were made prior to the passage of the legislation, i.e. you can own under federal law a "pre-ban" semi-auto with certain evil looking features. However, you might (if you live in California or certain other states) be guilty of a crime if you own such a firearm, even though it isn't a violation of federal law. It can be confusing, so you should write to both BAFT and your state attorney general letting them know the type of banned weapons you are interested in.
If on the other hand you are trying to find out about something else, say destructive devices, why don't you make out a third letter and address it to the Federal Dept. of Homeland Security. I am sure they will quickly respond to your inquiry on these banned weapons.
:lol:
