I know the routine for submitting a Form 1.  I have 4 approved.

My last one was a Spike's ST22 lower that I listed as a soon-to-be 5.56 SBR.  Got a total of 5 calls from the ATF for clarification as well as sending pictures of the receiver, but it was approved.

Now I have finished a British RSAF Sten Mk II kit and am finishing up a Polish PPSh-41 kit.  When I submit the Form 1's for both, is there anything special I need to add to the forms to clarify they what they are?  Like detailed build info and pictures?

Just wondering if I should provide more info than is necessary or wait for a call.

Are you talking about building firearms out of 80% receiver blanks (or from raw material) and then filing a form 1 to register it as an SBR?

If so, back when eforms was a thing, the direction was to use (FMI) as the manufacturer name.

I'm not sure if that is still the direction.  However, you might want to check the silencer BIY forum a few below this one.  The guys currently building form 1 silencers will know how to do the form.

As far as pictures or diagrams, I don't think any are needed unless ATF asks for them.

The issue with the Spikes is probably because the lower is marked as .22LR, and you are making a 5.56 SBR with it. Im guessing they were confused about that, and may have thought that you may have made a mistake somewhere.

Not sure about your next question. Are you making them from a blank? IE not a receiver that is already registered? If that is the case, you would need to do as the previous poster said about the FMI.

What is FMI?

The STEN tube is a reduced diameter tube from Indianapolis Ordnance,  and the PPSh is from a repair section from Hellbox Armory.

FMI is what one would use if making,
a suppressor, from scratch, or
if you make an AR from a block of metal, or metal plates, or plastic, or something that was not manufactured by a company and is not assigned a serial number, and you are submitting a form 1 on it.

I believe the FMI is/was only used for the Efile option, I'm not sure how the paper form was filled out if you make it from scratch as you are doing. Someone else will need to chime in on doing a paper form for making a sbr from a blank receiver.(IE, not from a manfg.)