The M20 SMG, unlike its predecessor, the M7 SMG, cannot be dual-wielded. However, it slightly makes up for this with the following:
The ability to be smart scoped, which reduces reticule bloom with an added cost of more recoil.
Increased damage, with the M20 SMG killing in 19 or 20 rounds, dependent on headshot bonus.
As of the November 2017 update, the SMG now deals bonus damage with headshots on unshielded targets.
In addition, its maximum ammo count was reduced from 420 (360 + 60) to 360 (300 + 60).
In comparison to the Assault Rifle, the SMG's ammunition is rarer in multiplayer and the campaign.
Short, controlled bursts with a single SMG is required to maintain ammo and effective range when engaging enemy forces.
Should the player be stuck with the SMG, the player should stay in close quarters and avoid going to a place where an opponent can kill them with longer-ranged weapons.
In Warzone, the SMG can be equipped with various attachments. The Long Barrel increases bullet magnetism and red reticle range, although the player would be much better off with the Battle Rifle or DMR. As with the Assault Rifle, the SMG is best equipped with Stabilization Jets or Laser Targeter for easier control of fully automatic fire, or Kinetic Bolts for additional damage to vehicles. The Silencer attachment is also a decent choice for more methodical players.
The M20 is great against jackals. Just shoot a jackal in the hand to make it stumble, and go for the kill.