Crysis Wiki

One of the series' defining features post the first game, ammo cases can fully restock the player's ammunition supplies for whatever weapons are being carried. In many other series, it's necessary to hunt for rare ammo, but not so in Crysis. In fact, picking up a defeated enemy's weapon will yield only a handful of cartridges, which, combined with the generally low maximum amount of ammunition the player can carry, further necessitates finding supply dumps, and hoping there are ammo cases for the weapon types you carry.

In Crysis 2, cases were limited to 'normal' ammunition and 'grenades,' with grenade cases being annoyingly rare. The third game adds special ammo cases, arrow cases, and expands usage of both the normal and grenade case. Whereas in the first game, using a normal case would refill your inventory, but not your weapon, all but forcing a reload and wasting another 'charge' of the ammo case, in Crysis 3, normal cases now reload your weapons, as well. Crysis 2's grenade cases are limited to frag grenades and certain rifle grenades, and only rarely come with more than a single charge,' whereas Crysis 3's grenade cases often allow 2 or 3 uses, reload all applicable weapons like the normal ammo case, and now hold all forms of rifle grenades and L-TAG grenades. In both games, each use of a grenade case allows the player to replenish 2 frag grenades.

Special ammo cases and arrow cases do what they say on the tin: refill 'special' ammunition, which includes the special ammo many weapons now have as one of their customization options, and various underslung mini-weapons. Arrow cases are the only way to restock the various special arrows for the Predator Bow, and these cases become rarer the further you progress into the game.