That’s interesting that the forcing cone cracked with 158 grain bullets. That is all I shoot in mine to keep that from happening. I generally shoot 1100-1200 fps loads in mine but not very often. Mine sees more .38 Special than .357.
When I was competing with the Model 19, it got shot alot. Over a 3 to 4 year period, probably 200-250 rounds per month. Max loads of W296 with 158 grain jacketed bullets.
During this time, 1980 or so, 158 grain loads in 357 Magnum were kind of the norm. The 125 grain loads were starting to become popular. Once the 125 grain loads took over in popularity, it is one of the reasons I feel that they got the reputation for cracking the Model 19's forcing cone.
In general these days, I load 158 grain semi-wadcutters to about 950-1000 fps in 357 Magnum cases for all my 357 Magnum shooting. I do not shoot my Model 19 much any more, shooting an L-frame instead. If I want to shoot a K-frame these days, I'm more likely to shoot 148 grain wadcutters from my Model 14 or Model 15.