The light bullet loads create problems for K-frame Smiths like yours because a 125 JHP (e.g.) accelerates to such a great speed by the time it hits the forcing cone it slams into it in a way that might eventually crack the flat-cut area on the bottom (look at where the 6 o'clock position of your forcing cone is thinner than the rest--an inherent soft spot in the K-frame design). Also, you get more flame cutting at the top strap just above the forcing cone with the explosive gasses such loads create.
My 66 is loaded for HD with 158 LSWCHP +p's (or rather, homebrewed equivalents thereof). For practice, I shoot standard pressure .38's in the same bullet weight (i.e., 158 gr LRN). You want to find a practice load that's at least close to the same bullet weight as your defense load, so they'll shoot to the same point of aim.
I don't like the 125's, myself. I think the primary reason for their dominance among .357 afficianados was the fact that early JHP's were relatively crude. You had to have a light bullet, so you could accelerate it over 1400 fps in a manageable load, so you could get bullet expansion. Modern JHP's--like the Gold Dot in 158 grs.--don't require this kind of velocity for good performance/expansion. In my 66, heavier bullets are more pleasant (and less flashy/bangy) to shoot, as well. If you want a .357 load (rather than my load, with which I'm very comfortable), I'd try the 158 Gold Dots or maybe Winchester's 145 gr. Silvertip--both excellent loads. For practice, find something with a similar weight in a .38, and have a blast shooting a wonderful K-frame.