How to carry two primary weapons in Modern Warfare 3

Source:

https://www.eurogamer.net/modern-warfare-3-how-to-carry-two-primary-weapons-mw3-9328

"To carry two primary weapons in Modern Warfare 3 you have to equip the Gunner Vest or Overkill Vest. The Gunner Vest is easier to get, as it unlocks at player Level 20, whereas the Overkill Vest unlocks at player Level 50."