40mm Flashbang ammunition is designed for use with a grenade launcher. On impact, it will emit a flash that blinds anyone looking at it.
— In-game description
40mm Flashbang is introduced in Battlefield 4 as a usable ammunition in grenade launchers.
The grenade acts in a similar manner to the 40mm LVG, being capable of bouncing off objects and players after being fired. Unlike the LVG, however, the 40mm Flahsbang has a very long timer if it never comes into contact with a surface, taking ten seconds to detonate. If it bounces of an object at least once, however, the grenade will detonate after one second, (Or two seconds if the grenade hits something within about eight meters of the player), blinding all nearby players in an identical fashion to the M84 Flashbang. This applies to all players within a seven meter radius of the grenade, though the effect deteriorates the further away they are, and lasts for a shorter duration on friendlies and the player that fired it. Like the M84, the flashbang will also cause a small amount of damage, about 5-3 depending on distance from the grenade, to enemy players and the shooter when it detonates. This blast is also capable of setting off other explosives in its radius.
Also like the LVG, the 40mm Flashbang is capable of inflicting direct damage, but instead of the LVG's 25 impact damage, the Flashbang causes 100 damage to enemy players, instantly killing them if they are hit in the torso or head. This applies to all impacts a grenade may perform; if it bounces off of a wall and then hits a player before going off, it will still kill the player. A player can potentially survive the impact, however, if they are hit in the legs or if they are using the ARMOR specialization, due to the .9 damage reduction in both cases.
Something interesting to note about the 40mm Flashbang is that, while it still cannot damage even lightly armored vehicles, it is capable of causing heavy damage to RHIB boats. One impact by the grenade can drop the boat about 20-30 health, taking around four shots to completely destroy it. If the player gets lucky, however, they can potentially land it inside the canopy of the boat, where it will keep bouncing inside of it and can potentially destroy it in one shot. Stationary emplacements, like the M220 TOW Launcher and the 50. Cal turret, can also be damaged and destroyed by the grenade impact.