Riverdog, the Model 14 is the standard .38 Spec. target model, with a six inch barrel. Great shooters. I doubt that Plus P rounds would hurt it.
Tator, I don't know what happened to your Model 15, but that was the standard issue handgun with the Los Angeles Sheriff's Dept., for many years. The last round they used before going to the Beretta 92FS, was the Federal 110 gr. JHP, a "Plus P" round, although not designated as such. (Had to be politically correct, for the Marxist crowd in L.A., who felt that if a cop had to kill a puke, it wasn't nice to kill him "too" much.) Federal guaranteed that .38 Spec. round from a four inch barrel at 1250 FPS. That round was the duty round, and no Deputy was allowed to carry anything other than that round, both in his service revolver, his backup .38, on or off duty.
LASD had nearly 10,000 of those Combat Masterpieces, and I never once heard of one blowing up, using factory "plus P" ammo.
Not that there can't be a flaw in the metal or something of that order, but a squib or double charge, can definitely ruin a fine revolver.
Hope you determine what caused your problem... and loss of a great revolver.
FWIW. J.B.