My 686 to 696 conversion has been fed a diet of 260 grain hardcast GC Blue Dot loads at 1000 fps for about well over 500 rounds.
No problems at all. It is still as tight now as when I built it.
Forcing cone cracking is more a function of the gun being out of time than anything else. A properly cut cone will support the bullet impact inside the frame an not on the thin edge.