Nothing related to muzzle loaders (legally considered an "antique" under the Gun Control Act) requires an FFL or any other licensing or registration. That covers most everybody here. Anything else requires an FFL. I turn down work all the time because it would require an FFL. In fact, I am getting a legal opinion right now as to whether I can even photograph modern firearms without an FFL. It is not as clear cut a situation as you might think.