It is very simple, the 38 cases are not designed for .357 chamber pressures.

The same applies to .38 revolvers and cylinder design.

I have a .357 Ruger Vaquero and the cylinder and barrel are much thicker than normal. And a .38 revolver would have a smaller diameter cylinder and thinner cylinder walls.

The reason I say this is I have been reloading for over 47 years and mistakes can happen. And a few months ago I had a double charge of 231 in a practice load for my Ruger Vaquero. I was very lucky the .357 Vaquero had a heavy duty cylinder designed around the .45 Colt. I had to pound this case out of the cylinder and it took a good deal of effort.

Bottom line, if you want to hot rod a .38 Special then buy a .357 that is designed for higher pressures. And not pound the heck out of a revolver designed for lower pressures.