First, I will confess that I have never done a controlled test to prove it, but I believe (everything else being equal) that light loads shoot higher than heavy loads at short range. It makes intuitive sense. As the bullet rumbles down the barrel, Newton's laws rotate the handgun before the bullet exits. The quicker the bullet exits this rotating platform the more nearly it flies parallel to line of aim. This is apparent if you look down the side of a .44 magnum to see where it aims and points. Line of bore is about a foot below point of aim at 25 yards if the handgun is sighted in at 25 yards. Of course a heavier load makes the pistol rotate faster, but the dominant factor is bullet residence time in the barrel before exit. Like many of you, I don't pay much attention to all this because of adjustable sight handguns, but now I have a Model 10 to play with and I just might do that controlled test to validate. Should be fun.