My Speer #10 book (1979) does not show a 170 projo but 4.9g 231 as starting with 158g LSWC, CC! 500 primer, 897 fps 6''Ruger Sec Six; 5.5g Unique starting 970 fps. A 170g projectile must be reduced from there.

My Lyman Cast Bullet Handbook #3 (2008) does not show any lead loads heavier than 115g #358345 with 231 using .357 magnum cases.

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