Editor:

1. Place a BLUFOR rifleman and make him player's character.
2. Place a BLUFOR rifleman, as your subordinate. Make him a playable character.
3. Place a Blue weapons box in close proximity (EMPTY/Ammo/[BLUE]Basic Weapons.
4. Place an OPFOR rifleman close in front of you.

Ingame:

5. Quickly shot the OPFOR rifleman.
6. Select the rifleman (key F2) and tell him to "Take Katiba", from the action menu (under key 6).

--The rifleman does as ordered and switches to pistol.

7. Tell the rifleman to "Rearm at rifleman", using the action menu.

--The rifleman acknowledges the order and takes the ammo.

Regardless of having the rifle ammo, the rifleman still uses the pistol. There is no command in the action menu to "use rifle/primary weapon" either.

8. Select the rifleman and switch to him. Open his inventory and see, that the Katiba ammo is there.
9. Switch back to the leader.
10. Point at the weapons box, select the rifleman and select "Inventory" from the action menu (sometimes it may be necessary to have him moved close to the box first). Watch the rifleman.

--The rifleman goes to the box and assumes "searching" posture.

11. Give him TRG rifle, with either right click or drag and drop method. Observe, that the rifle out of the box, doesn't have a magazine inserted.

--The rifleman says "out of ammo".

12. Using the same method, give the rifleman a TRG mag.

The rifleman reloads the TRG, and then happily switches back to the pistol.

Telling the rifleman to rearm at the box doesn't help either - he is stuck with the pistol, despite having a TRG with many magazines.