REPRODUCTION
"Ghost bullets/Blanks": While holding 'left trigger', press 'Y' [Surrounding players will hear gunshot, player reproducing will hear and see nothing] (this will cause remaining bullets in the magazine to become ineffective)
"Magazine Stuck in Gun" : Quick Reload magazines by pressing 'Y', then pressing any button during reload animation
"Magazine won't go in Gun" : MANY CAUSES Exchanging weapons between players, loading new gun with magazine by quick reload pressing 'y'
*EDIT* Not sure why I got downvoted for reproducing, I'll be sure not to help again :)