with a pistol i can shoot okay when the target is directly leveled with my eyes, however if i move the target a few inches above or below my groups opens up.

example, silhouette target, the chest is at my eye level, all the chest groups are nice, sometime a really nice hole, but the head target will be atleast twice the size.
if i place the head at eye level, the head will have a nice group, and the chest group will open up.

my grouping isn't effected by left or right, just up and down. I'm talking slow fired at 7 - 10yrds

anyone else has this problem, wut can i do to correct this.