are you sure? i think ive heard about bullet drop and my bullets tend to have quite a wide dispersion at the range, further out than the distance from where i aimed them.
That's just accuracy for you. Bullets generally have a deviation circle if hip-fired or after having recently moved whilst shooting, or aiming while shooting.
Most guns' ironsights has the top of the ironsight as the center where the bullet will generally land. If you line the top of the irons up with the middle of their head, that's where you'll hit.
There's no bullet drop.