The conicals must have come on the scene in the 70's or early 80's. Note, too, that round ball guns were probably used well after they became obsolete, as did flintlock rifle and shotgun continue in use after the 19820's.
: The paradox had rifled chokes with smooth bores and shot the short, pointed, shouldered slugs with one groove, used for an impressed crimp of the shell casing. I expect there was a lubricating disk below the bullet, between wads.
: It is said they didn't screw up shot patterns, which is difficult to believe as any rotation of the shot column would tend to spread it.