The Ammo Pack is an alternative resupply item for the Support kit in Battlefield 4. It provides some primary and secondary weapon magazines for the player that picks it up. It can supply explosives or replacement gadgets like the regular Ammo Box but only while stopping on it.
Like the First Aid Pack, it can be thrown much further than the Ammo Box by targeting an ally. The pack will hone in on the player, making it unnecessary to compensate for their movement.
If thrown at a player that already has their full complement of reserve ammunition, the pack will remain on the ground.