M1a question??

This may be a dumb question but Im a bit of a novice... Ive noticed that when the mag is out and the bolt is closed, the bolt seems to be able to wobble a bit when pushed from side to side. But, as soon as the mag is placed in again, the bolt assyembly is stabalized. I know this may not be the best description, but not really sure how else to describe it. Anyways is this normal? Just wondering why this would happen and does this make it neccesary to fire the m1a only when the mag is in? If you need me to clarify what im descrbing, please ask. Thanks