right but,
You are correct, but most of the kits come with enough parts for them to be legal. These kits weren't what I was talking about though. The poster was asking about building a gun, not putting on parts from a kit.
Now, you can buy 0% up to 80% frames and do the machining yourself or you can just make one from a set of plans and I thought this is what the poster was talking about.
They are legal to build for yourself by yourself as long as you don't intend to sell the gun. Lot's of people build their own guns this way and have a good time doing so.