The ammo bags work similary to medic bags. Hold them out and you will resupply yourself and anyone standing in front of you. Toss them on the ground and anyone who runs over it will be instantly resupplied. You get a point every time you resupply someone.

Be warned: enemies can use these, and if you are trying to hide, don’t throw ammo bags out, if an enemy has the 3d map turned on, a ammo icon appears on their HUD, even through a thin wall and will give your position away. Even more if you throw them you’ll cry out “get ammo here”, in any given language. Your enemy will be able to hear you, and find the perpetrator of their Zen-meditation.

Friendlies with low ammo will be marked in your 3d map with a bar indicating their ammo status, as well their icon on the mini-map will have a red glow around it. Its always a good idea to chuck a few ammo bags where a anti-tank defender is. They tend to run out of ammo quickly and will appreciate having the extra ammo around.