Texgun

I have heared that using a heavier bullet will make the point of impact higher at 25 yards than a lighter bullet. I went to the range the other day and used 230 grain 45's in my Para which has adjustable sights. Sure enough I adjusted the rear sight all the way down and was shooting about 4" high. I don't understand the physics/reason of wahy it wirks that way. If anyone would have time to comment on this please do. Thanks