.
Why not just buy a Marlin Guide Gun in 450 Marlin caliber? It can be handloaded to more than you will want shoot often and it will kill anything on the planet.
The Marlin 1894 action is too small for the 500 S&W and it would never withstand the abuse of the very short pressure curve produced by high intensity pistol cartridges of the size and pressure of the 454/500 family.
.
