So I have an SBR lower that I built and that was pretty simple. Get the lower, submit ATF form, and then have it engraved once you get it approved. What is the process of getting an already assembled complete SBR? I am planning on a 11.5" Daniel Defense.
Do I take the lower home and the dealer keeps the upper? At some point I need the serial number for the form. Also since I already have a stamp for a different lower can't I get the whole rifle and just keep the DD upper separated from the DD lower until it is approved and engraved? Then I can shoot the DD upper on my existing lower while waiting. I just send a letter to the ATF with the DD upper's caliber and length. Do I need to get an approved response back or is just sending the letter sufficient?

Thanks