Sorry for the noob AR questions, but here's another one
Assuming you have a place to shoot full auto, what would be the disadvantages to building your AR that way, other than having to pay the annual tax?
In order to build a full auto AR you have to have a full auto seer which was registered before 1986. It will still cost $200 for the tax stamp.
ALso, the federal tax is a one time thing for the tax stamp and is not annual. The MD ten dollar annual charge is not a tax it is a registration fee.