I know this is old, and I addressed this issue with you on another thread, but, like I am now, if someone is reading this later in time, I feel the correct information on “home-made” firearms should be included here.
One is legally able to sell firearms that are “home-made”. It is not legal to be unlicensed and be in the business of manufacturing and selling firearms. Does an individual need a license to make a firearm for personal use? | Bureau of Alcohol, Tobacco, Firearms and Explosives Further, on that link it states “In addition, the making of an NFA firearm requires a tax payment and advance approval by ATF.” That would mean that one is also legally “allowed” to manufacture NFA items, but not machine guns, will need a tax stamp (prior federal approval) to do so legally. Also, I have not found anything on the ATF site about the requirement to put a serial number on a home-made firearm before it is sold. How can I make and register an NFA firearm? | Bureau of Alcohol, Tobacco, Firearms and Explosives
This information on what is required/suggested when transferring a firearm in a private transaction: https://www.atf.gov/file/58681/download It does not mention that a serial number must be on the firearm. I could find no citation requiring firearms previously manufactured for personal use requiring a serial number when transferred.
This site states that a serial number is not required when transferring your home-made firearm, but I could not find a valid link to the ATF where it is specifically stated, except when discussing licensed manufacturers: Are Firearms without Serial Numbers Illegal? - Pennsylvania Law Abiding Gun Owner Blog
One other irony of our arms laws I just found while researching information on the ATF site, a Q&A fact: " Are muzzleloading cannons considered destructive devices?
Generally, no. Muzzleloading cannons manufactured in or before 1898 (and replicas thereof) that are not capable of firing fixed ammunition are considered antiques and not subject to the provisions of either the Gun Control Act (GCA) Gun Control Act | Bureau of Alcohol, Tobacco, Firearms and Explosives or National Firearms Act (NFA) National Firearms Act | Bureau of Alcohol, Tobacco, Firearms and Explosives. [26 U.S.C. 5845; 27 CFR 479.11] Last Reviewed April 20, 2020"
Are muzzleloading cannons considered destructive devices? | Bureau of Alcohol, Tobacco, Firearms and Explosives
So, an old operational cannon, that I would believe no one would claim to not be capable of horrific destruction, is not defined by the ATF as a destructive device, but a breach-loading cannon, regardless of size (apparently), is a destructive device. One has to love government logic.