Welcome to WaGuns.
In short, here's the process:
1) Submit (via eFile to the ATF) a Form 1. Await ATF approval of that Form 1, which will take a few months.
2) Get your receiver engraved with the required information.
3) Build the SBR.
A couple of things to watch out for....
- Here in Washington, we can't file the Form 1 until June 9th due to our recent Washington law change.
- The ATF process is going to change in July to require photos and fingerprints, so to minimize your hassle you should file before then.