I think this may have happened with 30 and 60 round mags but I can't be certain; I know that there was one instance where some of the emptied bullets from a 60 round mag went into my 300 round box and then 2 or 3 went into my inventory. I suppose that is a rather separate bug but it should be noted that I had 2 bullets left in that magazine before I loaded the rest so it seems that whatever data storage technique used for magazine capacity is faulty.