The S&W fixed sight revolver were designed to shoot 158 gr. bullets.
All else being the same, lighter bullets would shoot low, heavier bullets will shoot high.
I shoot both 150 & 158 gr bullets in my M-64 and the truth being told, I can't shoot good enough to tell the difference.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071