Seems like a troll this one...

Had something similar happen to me while in SP. I was walking forward and played with the "lower weapon" movement and suddenly I was just walking forward with gun lowered and not been able to do anything at first but change view and use free look (alt). Problem was only solved by weapon change from scroll menu from primary to secondary arm. After the weapon change things went back to normal.

OS: Win 7 64-bit

This would be a great feature to have and for the "eject" feature something like double tap "Reload" would do a quick pull back to get bullet from old mag out and first from new mag in..