I have been experiencing different bugs with overcharge when reloading and it usually only seems to happen with the pump shotgun. Most all of my experiences with this have been during pvp.

1)I will run out of my clip (ex 13 shots) then hit overcharge so i can then get my instant reload and have a full clip, yet my guy will continue to sit there and reload with overcharge wasting away.

2)A clip will go to 0 shots left, and i will begin reloading yet my shot count will not be going past 0 (ex; i would see him put in 13 shells yet my shot count shows 0), therefore i would have to reload again for me to have full ammo.