3.1 - 3.2 W231 is an excellent load for the 52 . Swaged HBWC's also are best . Unique is not the best choice for mid range loads in 38 special . I'd say 3.3 - 3.5 Unique would give same velocity ( 710 - 750 fps ) . For a cast WC I'd go a bit hotter ( 800 fps ) but no more than that . You can get heavier & lighter recoil springs from Wolff .