I am aware of a cracked forcing cone in a K-Frame .38 that was shot with standard .38 Special loads and it was reported on this forum although I have lost the thread. The handgun was already well shot before the incident occured.
It has also been reported here that another "suspect" of forcing gone cracking was leaded forcing cones that were not cleaned sufficiently.
Another suspect is the hard, ball powders which burn very hot, like H-110/W-296. And it is a fact they will affect handgun metal because these powders do cause visible wear on the top-strap (called flame cutting) and the outer edges of the forcing cone. Some of my K and N frames exhibit this.
And, as Sebago Son has illustrated there are K-Frames that just are not affected by cracked forcing cones with any load.
In Colts, the "D" Frames (if I have this right) as in the Police Positive and Detective Special have a thinner all-the-way-around forcing cone and I have heard, but have not seen, that they too can crack. What loads did it I do not know but when the +P .38 Special loads came out Colt did state not to use them in those guns.
I am not deep into metallurgy but I was once an aspiring welder with some college training in that direction. Even the best (back then) metal producing program can create odd, or indiscriminate examples that just won't perform as they should.
It is possible some of the K-Frame .357 barrels/forcing cones fell into that "genre", they just didn't come out as well as the others and were prone to failure.
My use, and I have a few K-Frame Magnums, is that I load .38 Special loads in .357 Magnum cases for practice. I load lead 158 SWC's to magnum velocities in .357 Magnum cases.
I see no advantage to a 158 grain jacketed bullet over a cast one in a K-Frame.
However the "non-reloader" has to use factory ammunition and as such, supposedly the factory 158 jacketed rounds "should" be safe in a K-Frame. There is a small variety of "cowboy" .357 Magnum loaded ammunition that is a 158 grain lead bullet at .38 Special velocities for the Cowboy Action Shooters as well. It should produce a 158 grian lead bullet at about 800 to 900 fps.
I will admit to being "bummed" by this knowledge. I specifically wanted to dedicate my K-Frame .357s to 110 and 125 grain loads going as fast as safely possible...
Their light weight would be well suited by the lesser recoil of the lighter bullets.