This problem is just about the animations, it has no change on the gameplay.

When you reload a Zafir or the MK200 or any box-fed machinegun for that matter, the reload is fine, but when you have under 10 bullets or you wasted all the bullets of the box and then reload it you will notice the animation in wich your hand put the first bullet of the new clip inside the chamber of the LMG doing it with invisible ammo, wich wont be visible until the reload animation ends.

This happends with the last 10 bullets too, not limited to having the whole clip wasted or having just 1 bullet left. I will try to upload a video to explain it better