I am a complete noob to this so sorry if this is a dumb question. I am planning my first build. Thinking about getting most of my parts from Spike's. My question is is there any legal forms that I need to fill out like for gun registration and what not? I know I gota have the lower sent to a FFL and I have one lined up. But ATF wise. Do I need to tell them i am building one or do I need to register it?