Dom20961,904,221 Locked 25 Aug 2009
To supply ammo packs, choose the Engineer class. Hit "Y" to drop an ammo pack. While anyone on your team can pick them up, try to target players with an "ammo needed" sign over them. These players have no ability to reload.
Upon spawning you can drop two packs. This ability will charge, allowing you to drop a new pack about every 30 seconds.
Just keep supplying packs, and you should have this in about 3-4 rounds.
Also, be aware that players on the opposing team can pick up packs you drop. Packs picked up by the opposing team do NOT count towards this achievement.