If you don't have confidence in a S&W's safety, and if no one has fired it like it is, you may want to contact S&W (800-331-0852) with it's SN. If new enough to be covered by their 'Lifetime Warranty', they may look it over for free.
Now - I have just shaken my only loaded revolvers, my CC & HD revolvers: 2" 10-11, 4" 64-8, 2.5" 296, & 1.9" 642-2. All rattle - the rounds are loose in the chambers. As others have said, that's normal.
I reload - and know why I re-size - it's to promote uniformity and a small enough size to permit easy reloading of even a moderately dirty revolver. I feel what you are seeing and hearing is normal.
Stainz