No hoops. You just cannot manufacture it "for sale" since you don't have a firearm manufacturer's FFL from the ATF or a regulated firearms manufacturer's license from the state. But it is not illegal to make it for yourself.
The federal law is 922(r) for compliance parts. It states basically that you cannot have more than ten imported parts in a rifle you assemble here which is banned from importation. Usually on AK's that mean six US parts, unless you have no muzzle brake or other muzzle attachment in which case it is five. Your receiver, and US-made hammer, trigger, and sear will give you 4. Add a ten dollar US made flash-hider for 5, and a two-dollar Tapco mag follower for six.
If it were me I would just spend the 55 bucks with NodakSpud and get a 100% receiver. Depends on if you have the tools and stuff you'll need already. The internet is full of "I built my AK in one morning before breakfast" claims but truth be told they're a bitch to get all the holes just right, the rails the right size and smooth, the lower bolt rails welded just so, and heat treat the FCG holes without warping the whole thing. You can easily go through 3 blanks before getting it right (ask me how I know
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