There was a whole thread of maniacs over on Calguns who built these Obrez. Basically, they all started with de-milled (cut into three pieces) receivers, you weld the receiver back together and voila, you have a pistol, not a rifle, not an SBR, no NFA, no tax stamp needed. And if you can have that in California, you can have that in almost any state.
Takes some skills in welding and fabrication but as the owner of multiple Mosins, I think having one of these would be a very cool range toy. Totally impractical but fun.