158 Grain is the ONLY 357 ammo that should be fired through a K-frame magnum, such as the 19, 66, 65, 13. The reason is that 125 grain 357s have a long history of cracking forcing cones in K-frames and there are NO remaining K-frame barrels left at S&W. K-frames have a flat cut out at the bottom of the barrel where the crane fits. This is the weak spot that cracks. This is the reason S&W came out with the L-frame magnums. I was told by a S&W technician that K-frame forcing cones have been known to crack within 50 to 100 rounds of 125 or 110 grain 357 ammo.The guns were designed at a time when police officers trained with 38 Special ammo and carried 357 ammo. The trouble started when someone got the idea that you should train with your duty ammo. There is no similar problem with 38 Special ammo.

I usually shoot +P38 Specials out of my K-frame magnums. +P38s will usually have less penetration and lighter recoil, thus being less of an over penetration hazard and having a higher rate of controlled rapid fire. So what good is 158 grain 357 ammo? It is the only 357 ammo that a K-frame ought to be shooting. If you are going to shoot a deer or some game animal, the 158 ought to do as well as a 357 is capable of doing.

If I need 357 type power, I usually switch to a 41 or 44 Magnum.