I have long felt that the K frame has adopted an undeserved reputation of being prone to FC failure. These concerns are some what misplaced and certainly misunderstood. First of all, S&W would not have continued to produce this design for as many decades as they did, if the design was incapable of sustaining the industry maximum for the .357 mag.. They went to some extremes to get to the bottom of the issue, and what they discovered was that, build up in the FC was the primary cause of excessive pressure induced damage to the FC. One particular misconception by many who shoot lead, is that after shooting lead through a firearm, one can just run some jacketed bullets through to clean most of the lead out. This is a big no, no, this only amplifies the risk, and not only with K frame revolvers. It doesn't take much build up to excessively raise pressures to damage it. Think of those deposits as an obstruction, cause that's exactly what they become.
I have shot thousands of full tilt jacketed 296 reloads, and almost exclusively through both of my 66's, with no sign what so ever of an impending issue. And although I don't shoot large quantities of 110 and 125 gr. jacketed 296 reloads through them, I have indeed put a few hundred through each of them. And as I stated above, the most important factor in avoiding FC damage, is making certain that the FC is kept free of any deposits, be it carbon, copper, or lead. Deposit build up is the primary cause of damaging pressures that induce FC damage in the "K" frame.
GS