You can send your friends common weapon XP cards through the Friends tab.
  1. Tap the two-person icon at the top of the main screen.
  2. Tap the XP icon on a friend's listing to send them a common weapon XP card.
Common weapon XP cards can be collected in the gift section of your mailbox.
  1. Tap the envelope icon at the top of the screen.
  2. Tap the gift tab to collect your common weapon XP cards.