To be a firearm dealer you need an FFL license, but there are no federal laws against making your own firearm (as long as it is not restricted by the ATF, such

To be a firearm dealer you need an FFL license, but there are no federal laws against making your own firearm (as long as it is not restricted by the ATF, such as select fire, or destructive device or something). States may have their own laws against firearm manufacturing.