Unlimited ammo but 50% less damage blocks 2 backstabs because well look its steel slows heavy down to ownly spin up walk speed and when spined up cant walk but when spined up 50 more health also when backstabed twice you lose all debufs and buffs also melts spy cicle when you still have the back back also slower sandvich no ammo or health from dispensers while back pack is on when off though you can get your ammo refilled with back pack slower medic healing when backpack destroyed 10% more damage than brass beast but only 150 bullets