Which gun does the Double Duty talent affect?

While holstered, reloading from empty gives you a 20% of your magazine back as free ammo. Can occur once every 30s.

Does this give the gun you're reloading from empty the free 20% ammo, the holstered gun, or maybe both?

Haven't gotten the talent to test myself, but I'm curious because I was taking a look at the Measured talent and thinking that if it affects the holstered gun it could be pretty interesting in a weapon swapping build.

Double-Duty: While the Division agent has this weapon holstered, reloading the other main weapon also reloads this one. (ar, smg, lmg, bolt-action, sg).

Source, source and video.