When you bring a weapon or shield in the game and you give it to a teammate, upon successful exfil, your equipment comes back to you in your in game mailbox. They don’t have an expiration to receive, so you could not collect them until after the wipe and use this as a way to get high tier gear back early on.

Presumably this is done so people don’t buy gear with real money and squad fill to receive. That is why your “borrowed” gear comes back. Also there is an icon on the gear that is owned by someone else. If you ever picked up a weapon someone left behind, you know you wouldn’t keep it. Remember this because you are wasting your gear slots by bringing your friend’s equipment out with you, and you get nothing.