Geeze I learned how to do that 22 zip gun when I was in junior high. Isn't it or wasn't it illegal to posses one? Can't recall.
I know in highschool I got a hold of a copy of the Antartist Cook Book. Think it had zip gun and all the other fun stuff weren't supposed to play with.
Mac
a pistol needs to have rifling , and a rifle needs to have a 16 inch barrel
a 16 inch barrel 22 rifle can have a smooth bore but not a pistol
so it puts you in NFA territory if you get your length wrong so not illegal to manufacture just illegal to not register/ pay the illegal tax on it. if you make it too short .
illegal tax or not the tax man wants his pound till someone ends the illegal taxation