1. Choose a primary of your liking via the car (grab a secondary as well)
2. Switch to your secondary
3. Unequip your secondary via car
4. Your primary will now appear in your secondary slot, resulting in having 2 primaries at once.

Additionally, there is no need to equip your secondary once again if you want to dupe another weapon. You can simply switch to the weapon in your secondary slot and choose another primary via car. This also means that you can have combos, such as Revenant + D&T, etc. etc.

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