Changing/adding different barrel length?

[MH64]

OK, my form 1 has just one barrel length listed. What if I want to add a different barrel length upper as well or change the upper to a different barrel, what, if anything, do I need to do as far as paperwork since my form 1 originally had say a 10.5" barrel?

[markm]

My only concern would be going shorter. If you want to run an 11.5 or something, just put it on.

I have an SBS that I bought. It's registered for a 12 inch barrel, but I like the 14 inch remington factory barrel better. So I just swapped it out. I don't ever shoot it anyway...