“You can make a 100% receiver ONCE legally, but you can never sell or transfer the gun.”
Actually, the law says you can not make a firearm with the INTENTION of selling it unless you are a licensed manufacturer,bla,bla,bla.
Very similar to all those folks that pledge “till death do you part”, their “intention “ was forever, stuff happens.
I am not sure that you can even leave the firearm to someone in a will.