1. Get two weapons of the same type (I used the SKS).
2. Put one weapon in your inventory, take the other one in your hands.
3. Load the weapon in your inventory.
4. Put every bullet that could fit the weapons out of your inventory (I'm not quite sure if that's necessary, but I did it that way).
5. The reload sign should appear. Just press R to reload the weapon in your hands.
6. If you look in your inventory you should see that the weapon on your back is still loaded (one time it showed that the weapon was empty, but when I relogged the weapon was loaded once again).
7. Eject the ammo from the weapon in your hands and start again.
8. If something wont work, eg you cannot fire the weapon that was on your back or it shows that the weapon on your back is empty, just relog and your ammo should be cloned.