mm, Glad to hear you're OK and every one else also. Using Universal, max load appears on the Hodgdon web site as 5.6 grs. Were there ever any indications of an over pressure/charge with your reloads? Primers, cases sticking?
I would think S&W would want to look at the gun, could be a case of metal fatigue/failure and not your reloads.
Again glad you are OK

Bill