Think of it this way. If you take two lasers and mount them 2 inches one above the other and aim them at a point on a window you will see that top laser and bottom laser meet at the same point on the window but the top laser will continue downward beyond the window. Any point in front of the window the top laser will be higher than the bottom laser. Now if these two lasers were the barrel and scope sight on a rifle you can understand the correlation of the visual aim and bullet travel.
Now open sights (Because they rest right on top of the barrel) have less of a parallax or space between them and are a little more true to the aiming point.
It all comes down to how steady are you when aiming. How well do you know the drop-off or firing point of your trigger? Some triggers have a little creep before the actually fire some don't (Known as Hair Triggers.) Do you know how to breathe when shooting?
Remember new Air Rifles usually take 100 to 200 shots before they settle down and shoot consistent. The type of pellets makes a BIG difference. I don't recommend the GAMO Raptor, they are very fast but are too light and have a tendency to wander off target in a slight breeze.