I think I've got my process worked out.  Sorry if this seems pedantic, I just don't want to get it wrong.  I'm looking to file a form 1 to create an SBR from an AR pistol.

1.  Send lower for engraving.  Engraving will have my name, city, state, and caliber.  (Question: for a metric cartridge like 9mm, should it say Cal 9mm, Cal 9x19, or something else?)
2.  Get passport photos made.
3.  Get finger print cards and get prints made (question: can I take my own prints, or do I need a LEO to do it?)
4.  Fill out Form 1 packet as described in stickied post in this forum.  (Question.  With ARs, the general rule on overall length is 19 inches plus barrel length, but this is something of an estimate.  Should I err on the side of being short or long?  Related question.  Since I'm doing a 9mm AR, 9mm AR barrels tend to protrude about 1 inch shorter than their measured legal length, unlike rifle caliber AR barrels.  So in this case would I estimate OAL at 19 inches + barrel length - 1 inch?)
5.  Send both ATF copies to ATF by registered mail, with $200 money order, passport photos, and finger print cards enclosed.  (Question: Do both ATF copies need attached passport photos and finger print cards?)
6.  Send CLEO notification form by registered mail to a CLEO in my jurisdiction.  (Questions.  I live in an incorporated city.  Do I send notification to my city's chief of police, or the county sheriff?  Does the CLEO notification form require passport photos and finger print cards?)
7.  Wait a really long time.
8.  After waiting a really long time, stamp comes back in the mail.  Purchase a buttstock and attach to AR pistol to make SBR.
9.  File 5320.20s for each state I travel to frequently, fill them out to be valid for any journey within the next year.  (Question.  Does an approved 5320.20 work for more than one trip within the specified time period, or do I need one for every excursion across state lines with a registered SBR?).


Additional questions.

I see you guys receive some kind of status update on the status of your Form 1s.  Is there a way to do this online?

Is there a way to get certified copies of the tax stamp?  I'm thinking of putting the stamps in a binder that I can carry with me, but I'd like to have valid copies stored in a safe deposit box somewhere else.  Related question, is there a way to receive a stamp electronically, rather than physical copies?  Would be easier for archiving necessary paper work.

For 5 and 6, you don't have to send registered mail - but if that's your swerve, then spend the extra to get your mailing receipts.

Engraving doesn't have to be done before the application - you can engrave at any time prior to assembling the finished SBR.

I recommend you paperclip the pics and cards to each original form. ATF will glue the photos on for you.

Use your best estimate of the OAL, using the barrel length you intend to first make it.  If it no longer matches the description, it's no big deal and there's no requirement that it stay the as-built OAL or barrel length. You can go longer or shorter with no notification.

ATF asks that you notify them in writing of any permanent changes, but cannot legally require such notification. What's "permanent" on an AR platform, really, anyway?

ETA additional questions:

You can request certified copies, but they're no more valid than a printed scan would be. You can only get a virtual stamp (PDF file) from the .gov by filing an E-Form 1, which is currently no longer an option. Online status updates are also only for E-Forms at this time.

When you get your approved forms, scan them to PDF files. Stick the originals in the safe or safe deposit box or whatever, and make reduced size printouts of the PDF scans to carry with you, if you want to carry them around.

There is a common thought that getting engraving done before submitting the form is a good idea, because if any engraving mistakes are made, lost in shipping, etc, you can re-try before putting the manufacturer serial # on a Form 1.
But as the other poster said, all you have to do is engrave before assembly.

Good info.

When you say the other two copies are populated....is there an electronic version of this form that is filled out on a computer?  I was under the impression you just did it by hand three times...

The fillable PDF versions can be downloaded from the ATF's website. Then print them out, sign and date.

File on line. Efile.  

You can take your own photos.  They just need to meet the color and dimension spelled out for a passport photo, no glasses, etc. 

Engrave anytime before your stamp comes in, or do it after if you can engrave it yourself.  

F1 and F4 are not available on Efile since 41F went into effect.

Going to have to disagree with that.  Been reading the F1, and that's not clear at all.  In fact, the instructions seem to indicate to me that CLEO copy includes photos and print cards.  From the F1 instructions:

I can see how you would read it either way, but it doesn't strike me as being particularly clear either way.

So, how are we reading this? Photos and FP cards to CLEO or not?

I don't think you have to engrave caliber. If your AR receiver already has caliber (which most do), ATF allows you to "adopt" the factory markings for serial number and caliber.