Before the introduction of the 480 Ruger, a few prototype rounds were made headstamped 475 Ruger, but the idea was dropped and the 480 was adopted instead. There is very little difference between the 480 Ruger (1.3” case) and the 475 Linebaugh (1.4” case). The 480 Ruger can be fired in the 475 Linebaugh but not the other way round, much like the 38 Special and the 357 Magnum. It might have been the reason that the new Ruger offering would be different to avoid accidents if 475 Linebaugh cartridges were fired in the 480 Ruger chamber.