Dangerous game to play. Garland will send his FBI and ATF nazi thugs to arrest the guy for gun trafficking even if none of them are functioning. The ATF has no problem rewriting rules to create more criminals.
If a person is manufacturing guns, they have to serialize them and have a Type 07 FFL license for that manufacturing. Failure to do so opens up the printer to Federal charges.
You can make them for your personal use, and not have to put serial numbers on them at present. They cannot be legally sold or distributed (transferred) AFAIK.