one of the post under the vid sugest the original concept was using paradox rifling if I understand him right
" the model 1887 was originally designed as a 12 gauge shotgun. The 70-150 cartridge was a “wildcat” designed by necking down a full brass 12 gauge casing. In the original models, only the last few inches of barrel towards the muzzle were rifled. I don't know if your reproduction example follows the original pattern or not. This rifle and ammunition was never sold commercially, and I don't understand why Winchester even developed it. "

wonder why nobody starts making barrels for the common shotguns. when also making die sets for a reasonable price I am sure it would find a lot of interest.