A word on crowd control effects
While the stagger mechanic is barely described, it's one of the most important in the game, and it can be summarised as "stun that also removes protective effects".
As such, each time you manage to stagger your opponent, you're being given a short time window where you can fight and they barely.
Because of this, Stagger forms the foundation of pinning the opponent down so that they fail to take cover before they are finished.
Stagger chance is influenced by:
> Appropriate stagger perk (shotguns - enforcer, rifles - tank killer, heavy - one man army)
> Weapon defined basis (generally speaking, the heavier the weapon 'seems', the heavier the stagger, and this data might be stored at ammunition level, not the weapon level).