When the bullet leaves the barrel, due to bullet's spin inside the barrel caused by the barrel's twist, the bullet will have a little tendency to go towards the right/left of the barrel. In most cases, the bullet goes towards the right, since most barrels are twisted this way. This results in the bullet to land over to the right of the aim center. However, this effect is extremely minimal, only couple of centimeters in hundreds of meters of distances. In RSB, this is simulated as well, by checking or unchecking Affected by Spin Drift checkmark, you can determine whether this will be used or not.
Spin drift effect in 1000 meters.
Less powerful cartridges such as 9mm are affected much more by spin drift.
Let's enable spin drift on our Bullet Property used for this tutorial before continuing the next sections.