SBR & SBS and Interstate Travel Under the NFA and ATF Regulations

If I put my original barrel back on my SBR or SBS, can I take it across state lines without using an ATF Form 5320.20?

If you no longer own the barrel, you can do this, but if you still own or possess the short barrel, the item is still restricted by the NFA unless you remove the item from the NFA by contacting the ATF.