Short Barreled Shotgun with 18" barrel?

[Infi-del]

I have a question. If I register my shotgun as an SBS, I know that I can't take it into another state in that configuration without a big headache involved.

But if I put an 18" barrel on it... can I take it freely from state to state? I guess my question is what makes it a problem in another state... simply the short barrel length or the fact that it's registered now?

 

[Radar363]

Put the 18 inch barrel on the receiver, leave the short barrel at home.
The receiver is engraved but isn't married to a short barrel, same as AR's.