AI Bag Switch is a new item available in most CF versions. It can be obtained via the AI Farming System.
This item will let players to switch bags on-the-fly in Assault maps, regardless of where they are and whether they have used their weapon or not. If you are fending off a bunch of zombies and your rifle runs out of ammo, just press B and switch to another bag, and you can keep fighting without having to visit the ammo supply station. Another advantage is the ability to utilize your AI/TH Grenades - if you have 4 AI grenades, you can use ALL of them by switching bag, and then you can pick up 4 other TH Grenades for your 4 bags to use later on. Refilling ammo for the current bags will also refil ammo for all other bags, but the weapons on your current bag must not be fully stocked.
The only drawback is players cannot drop their weapon while using AI Bag switch. As most CF version won't allow Black Market guns to drop when players get killed, this mean you cannot share your weapons with your teammates before you lose a life.