In my experiance and humble opinion ..

Standard factory 125 gr .357's.are not going to hurt a clean, well maintained Smith and Wesson K frame.
Dirty Guns and superman loads have in the past caused issues with a few model 19's..pre -4's if I recall correctly.
The Barrel has .357 stamped on the side for a reason.

The 158 sp should get the job done for self-defense..it will penetrate and as with all ammo used you need to be aware of that point.

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John 3:16