The Incendiary Rounds were a Division Skill featured in multiplayer, exclusive to the Expeditionary Division for Shotguns. The player was given 4 rounds every respawn. During the WWII Private Beta, the Incendiary Rounds were loaded into the weapon when the player spawned. This was changed such that the player had to manually load the shells if they wanted to use them.
Incendiary Rounds deal less raw damage than regular ammo , but they cause a burning effect after hitting a target. Although the Incendiary Rounds can still kill in one shot (due to burn effect), there is usually enough time for a skilled player to kill the player using the Incendiary Rounds with any weapon before they burn to death , essentially trading kills. Targets using the Armored Division will usually require two shots to kill them due to them taking less fire damage.
On April 10th, 2018, the Incendiary Rounds were removed from being a Division Skill of the Expeditionary Division became an attachment for any shotgun with the Divisions Overhaul. 8 rounds (7 for Combat Shotgun) are now given on every respawn instead of 4, the range reduction was reduced from 15% to 10%, and the Combat Shotgun now unloads the regular ammo to load Incendiary Rounds faster.
When the Divisions Overhaul was introduced, Incendiary Rounds allowed the Combat Shotgun to fire rapidly. This was patched after a few weeks.