Whats up guys,

This past weekend I missed another deer![:@]I know my rifle is on at 100 yards, the deer was only about 80 yards tops from me. I was hunting out of a blind, had a good rest and the shot was slightly down hill. I'm using 180 grainwinchester ammo.
My questions is should I switch to a smaller grain? and how low should I have aimed at that close of a distance. The other deer I shot at was alos about 55-60 yards. I know I'm not moving when I shoot, I love to shoot that gun cause its the smoothest rifle I have ever had.

What the hell am I doing wrong here? Any help would be greatly appreciated so thanks in advance.