So Bill Jordan designs the K frame model 19 with S&W. They took a K frame .38, slightly lengthed the cylinder to accomodate .357 rounds, and used a different heat treating to withstand the higher pressure .357. Jordan used to refer to it as a ".38 that can shoot .357 for business".
Since Bill Jordan hailed from the USBP, the USBP bought thousands of Smith model 19's. Many of those same model 19's were still in service into the 1990's and shot just as well as when they were new. Do NOT believe everything you hear about the K frame being "weak", many of those revolvers had 10's of thousands of magnums through them.