in a Senate judiciary hearing by first debunking the term:

“Firstly, I will not be using the term ghost gun and that’s because as a historian I try to be as precise as possible and the term is used more as a rhetorical tool, a marketing tool and because of that, it can create a false sense of authority on the subject,” Hlebinsky told the senators."

then she describes the usual and common or customary development of privately manufactured firearms:

“But the big takeaway about the history is that these privately made firearms have been around for centuries, basically since the first system was developed over 500 years ago,” she said."

more here:

https://www.ammoland.com/2021/05/gun-hi ... 4-20588801

Great article.