If I equip a gun from the Supply Locker it should be fully loaded by default (if the ammo is available). Likewise, whenever I store a gun into the Supply Locker, it should by default have ammo removed and added to the ammo pile of its type.
Again, this just removes extra steps from the user to manage inventory. You almost never want an unloaded or half-loaded gun equipped. There is no benefit and an obvious drawback. You almost never want a loaded gun sitting in inventory that you aren't using. But you may want to use the ammo in that stored gun for another gun. There is no obvious benefit to having loaded guns stored in inventory (especially if when you equip guns from the Supply Locker they are automatically loaded).