1. Place the weapons/items you want to duplicate in your inventory (cannot have them equipped).

2. Back up your saved game. This is the crucial step for the duplication exploit. Find the filepath where it stores your saved game files. Copy the saved game file to a different folder.

3. Load up the game again. In pause menu, select Social -- Mail (fourth tab) -- Send Mail -- Select Item -- Select Recipient -- Confirm Sending Mail.

4. As soon as the items are sent, exit the game and copy the saved game file from the backup folder to the original save game file path.

5. Send the same item(s) as many times as desired by repeating Steps 3-4. Note: If you send a lot of mail, there will be a one hour cooldown before you can send new mail.

6. The receiving player needs to go to Pause Menu -- Social -- Mail -- Accept The Mail.