agree with gunnut69, the rear sight is not the place to cut. Particularly if the sight is already bottomed out. You want all the notch depth you can get to get a good sight picture. A lighter bullet will 1. shoot flatter, and 2. not rotate the barrel as far before it gets past the muzzle. Install a higher front sight. Before cutting anything, like a now too high front sight replacement, I would move the rear sight up some clicks so you have some adjustment left once zeroed with your current load, to allow for adjusting to different ranges, bullet weights and loads. Then measure your bullet impact point on paper and calculate the error. Shooting to the The left might be your grip. The gun will recoil toward your thumb if you are using a stronghand only hold, should center better with a two hand hold, and shoot to the right with a left hand only grip. Make sure the barrel is screwed in to a sights straight up position. Grip tight enough the gun can't move from the trigger-pull, as the gun may weigh less than the triggerpull, it can move in your hand if you jerk the trigger, and/or grip too loosely.