Yes it's legal. However you're not supposed to manufacture firearms without a "license" from the BATFE. So you are allowed private sale of your firearms you no longer need. Of course this being constitutional Supreme Law (Article VI) trumps any unconstitutional locale law legislated and or enforced by ignorants. That said many locales have unreasonable and unconstitutional laws on the books.Is it legal to sell a homemade weapon? I'm not sure it can be sold if it doesn't have a serial number!?