Unless something has changed... And it may have...
But just an FYI. We all, myself included, often say buy an upper. Buy a lower. Put them together.
FYI you are avoiding a tax that way and technically if you ever sell the gun, I believe its supposed to be paid.
We never worry about it since I don't believe in selling guns.
If its changed please correct me. But if not just be aware. These are strange times.