SBRs are relatively simple, you need Form ATF F1. Application to make and register a firearm. You have to have local LE approval like any other NFA firearm. You then mail your application and photo along with your check to the dept of the treasury. You wait for however long it takes them to get your papaerwork processed anywhere from 2 months on...you will then get your form with a $200.00 postage stamp on it or your returned application with the disapproved box checked.