Like said above, no need for a magnum primer with W231. If you're looking to use W231 for a 158gr LSWC in a .357 Magnum go for it. Of course you won't achieve maximum velocities but then again, you are shooting a lead bullet. you can get 1,000 fps from that combination and even more with a harder bullet.

__________________
Freedom is never free!!
SWCA #3437