One important issue you need to consider is the preservation of the chain of ownership of the firearm if it is ever used in a crime , especially a homiside.
If you have a paper trail that the gun left your hand , legally to a new owner, whose identity you can confirm, then you may be held harmless in any litigation , which could be costly, that is a consequence of the crime.
The idea here is the C Y A approach...
My suggestion is to go through an FFL when shipping to a new owner......the $20 bucks is cheap insurance in my mind...FWIW...