The ammo box glitch can occur when you have two or more of the same weapon (with or with out the same modifications) in Fireteam Mode. What happens is that any ammo boxes (dropped by fallen opponents) that are picked up contribute to the ammo total for the instance of the gun that you are not using (for example, you have an M4A1 in your Primary slot and another in your Backpack, but all ammo picked up contributes to the ammo total for the one you are not using, which is probably already at maximum). This denies you the additional ammo, and also denies it to your teammates because you picked it up. You can still run over as many yellow boxes as you want, but you will only take them all, get no ammo, and leave none for your allies. If you take a red box, both guns (the one in the slot and the one in the Backpack) will be replenished.
