If you want to have a long gun with a barrel shorter than 16" you will need to complete a form 1 application. However, depending on the gun, you may be required to have some markings engraved.

Here is the deal, if you buy an SBR that was classified as an SBR by the original manufacturer, you do not need to have it engraved. An example would be a Spike's Tactical Compressor. It is designated by ST to the ATF as being an SBR. No engraving necessary.

If you are simply adding a short barrel to an existing long gun, you are required to engrave your name, trust or corporation name along with your location. Why? Well, according to the ATF, you are "manufacturing a short barrel rifle." As the manufacturer, you will have to leave identifying markings. There are some exceptions to this.

If you are applying as an individual, which I advise against, you will need your full name and location. If applying as a trust or corporation, then the trust/corporation name along with the location must be engraved as well.

The engraving must be done on the receiver (which contains the serial number) and it must be easily viewable. DO NOT engrave the barrel, or other parts of the gun that easily removable. The engraving must meet certain specifications. Engraved characters must be to a minimum depth of .003 inch and in a print size no smaller than 1/16 inch. If you have the engraving done by a professional, most people will not even notice it as something that was added after the fact.

You should also consider when to do the engraving process. You may also wish to see info on background checks when submitting a form 1.