It's a 1917 and has to retain the case mouth head space with a .453 maximum dia cast bullets .
The 45 mag dies came up dirt cheap compared to the Colts dies I looked up yesterday........ $75 !?! I only gave 25 for the mag dies .

As a plus I can hop the S&W up to +P+ like 18 kpsi and be well into standard Colts loads and nowhere near the working limits of the 1918 N frame .

Added cool factor for having a 45 S&W S&W that will run 5 cartridges with data and even the hot one is safe in the no heat treat do to jump and throat length dropping pressures .