Wait until you ever need to make an insurance claim.
They will not pay.
BATFE also says you must declare to the shipper.
Let alone violating the "contract of carriage" you agreed to when you signed the shipper form (but never read).
Actually, that was a joke. I don't use FedEx for long guns and USPS doesn't ask. They just want to know how much to insure the package for.
Rick