I was practicing trigger control with my M&P Shield today and I was aiming at the bulls eye but putting my group about two inches to the left in the straight line. I felt my trigger control was pretty good and my sight stayed on the bulls eye. Another shooter noticed and suggested I adjust my rear sight to the right. Do you also suggest this? Visually, the sight looks centered already. Wouldn't I also need to adjust the front sight and I would need a special tool for this, correct?