AK-47 Parts Kit with Auto Sear Legality?

[Orion]

Quarterbore,
In preparation for my first AK build I was thinking about the fact that essentially I am building an unregistered firearm from a bunch of parts. As long as the firearm doesn't violate the NFA and other laws restricting firearms doing this is perfectly legal.

Is there anything prohibiting one to build, for ones own personal use, a firearm from a bunch of parts of different origins? For example if you bought a barrel and machined up a reciever to fit it, either bolt action or semi auto, and then added on a trigger group and stock of some type? Would this firearm require registration under the current system?

Thanks

Orion