Hello folks, this is my first thread start so kindly advise me If I'm not doing it correctly.

I have a Navy Arms/Pietta Dbl. bbl. with two sets of bbls. One is very nice and the other is FUBARED 14" up from the muzzle.
My question is may I cut the damaged bbls down to 14" as It's percussion and not be in violation of having an unregistered SBR ? I am thinking that I would be GTG, but would like to hear opinion here before I plug in the chop saw. Thanks in advance, and glad to be here.
Thanks again..question # 2.
Since a damascus barreled pre-1899 ctg. shotgun is an "antique" in legal eyes, would the same hold true for it?