The chapter below contains information regarding special ammunition - which weapons can receive this ammo and if there is any other way you can lose it beside shooting. The guide for The Division 2 will help you solve all unknowns regarding special ammunition.
The Division 2 contains special types of ammo that are impossible to craft, but you can find them during missions. You can find it in chests - when searching through such chests, the weapon that you have currently equipped will equip the special ammo. Most of the time, you receive 30 bullets (the screenshot above shows the amount of ammo and its icon). Such ammunition mostly sets targets on fire, sometimes you can encounter shock ammo.
You cannot switch between normal and special ammo - you need to use it all. If you want to switch the weapon with special ammunition to the weapon from your backpack, you'll lose the ammo. The game informs you about this with a message.
Even if limited in amount and you cannot keep it for later, special ammo is very useful when fighting opponents. It deals average damage, but the placed effects open up the enemy for further attacks, e.g. when an enemy is set on fire, they stop firing to put the flames out. The ammunition is very useful when fighting more powerful opponents e.g. Elites (golden enemies) - you buy some time and can deal with them much faster. The ammo is less effective against heavily armored opponents (you need to destroy some of the armor to reveal weak spots).