From shooting my FA 454, BIG difference point of aim between a 454 bullet coming out the barrel at 1700 - 2000 fps and a 45 Colt coming out the barrel 800-1200 fps. my experience is 6"-8" difference at 50 yards, both bullets 260 gr. I Haven't tried this, but if you maintained muzzle velocity, would changing bullet weight change point of impact? That may be a way to download for practice without messing with the sights.