The M320 HE is a grenade launcher with multiple capabilities that is available for use by players using the Assault kit in Battlefield 4. It is classified as an underbarrel attachment that can only be used on ARs equipped with either UGL or an Underslung Rail. This gadget is available by default and has a few different variants.
The M320 HE fires a single explosive round (a 40mm grenade). The weapon is designed to be used on small clusters of enemies or on small vehicles. It is capable of decent damage but is only effective at close range. This is useful for protecting an objective that multiple enemies are trying to take or even wiping out a room with multiple targets in it.
The M320 SMK variant fires a smoke grenade. This ammunition type is great for concealing teammates while they capture a point or for providing cover while on the move in a location that is being watched by the enemy team. Smoke makes it impossible for hostile players to spot you or your teammates.
The M320 Dart variant fires cartridges of small, needle-like projectiles. This basically converts the M320 into an odd shotgun. It is best used at short to medium range encounters and deals a moderate amount of damage. It works well for getting a quick kill when you need to reload your primary weapon.
The M320 FB variant is capable of launching flashbangs at your enemies. These don’t travel very far but work well for blinding opponents that are setup in hallways or small rooms long enough for you and your team to rush in and kill them. Don’t fire this randomly, be sure to strategize with your team where and when you should fire them.
The M320 LVG variant fires timed explosive rounds. Because they have timed fuses these grenades are capable of being bounced off of walls or other objects. So if there is a team camping around a corner and you can’t fire directly at them you can instead fire a grenade to hit a back wall and ricochet toward the enemy team.