
Mobility effects are additive, but under the game's default settings, they always sum to 1, and hence simplify out to being ignored if the appropriate game settings are tweaked, they can be used to apply different penalties across walking, running and remaining still. Accordingly, doing both reduces spread by 79%.Using Aim down sights reduces spread by 65%.The exceptions being weapons with 0 spread.

Therefore, no matter how skilled you are with the weapon or what perks you have, your weapon will always have a slight amount of spread. The total spread is the largest of the aim spread value due to the character aiming and the weapon spread value due to the weapon itself.
