I have been loading the 357 magnum since the late 60s. No this doesn't
make me an expert but I have learned a few things over the years.
Magnum performance out of a 6" 28 means 1400+ fps with a cast lead
bullet with lubrication grooves and a crimp groove that you have heavily
roll crimped the case mouth into. 15.0-15.5 grs of 2400 with a magnum
primer. Winchester is my favorite. This load was basically the standard
full charge load for many years and will not batter your 28. Forget 4227
if you want the magnum in the 357. 296/H110 will give you the illusion
of magnum with flash, blast and face stinging spitting from the brl/cyl
gap but the numbers on the chrono will be lower. That's about what you
can expect unless, as mentioned above, you go to the 8 3/8" barrel 27.
296/H110 creates more forcing cone erosion than 2400. If you use
std primers and plated or jacketed bullets expect much less velocity.