Found a new reloading bug:
If hand 1 has 10mm SMG with 30 ammo loaded in it and Hand 2 has M3A1 (Grease Gun) with 0 ammo it is impossible to reload the Grease Gun, even when there is enough .45 ammo in the Inventory (it will play shoot_empty sound).
If at least 1 bullet will be shot from 10mm SMG, it will be possible to reload the Grease Gun.