It would not be my first choice to use 231 for 357 Mags if you want real 357 level loads approaching factory levels, primarily because it produces much higher pressures for less velocity than many other excellent choices in magnum powders.
However, if your intent is to develop loads more in the old 38-44 range rather than full on Mag levels, it certainly will do it.
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" I said, good DAY! "
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