Please, can we understand the OP only wants 38 SPL +P level loads, not 357 magnum level loads.
If Elmer Keith and Dick Casull had listened to half the prohibition sentiments in this thread where would the state of handgunning be today? A S&W M14 is a quality 38 SPL not made to any less a standard than a M15. M15's are rated for +P ammunition. The OP is not asking to make it into a 357 magnum or use it as such.