As someone else has said here: If mine didn't rattle, I would be worried. The rattle you are hearing on your 629-6 is coming from the hammer block safety. You can see this part when the hammer is locked back. It looks like a little metal flag, with the flag pole riding inside a slot on the right side plate of the frame. When the trigger is pulled, this little part drops down and allows the hammer to strike the floating firing pin that is built into the frame of the revolver. If the trigger is not pulled, the part stays in place and thus prevents the hammer from falling on the firing pin and in turn prevents the weapon from discharging.
Unless you are mechanically minded, I would recommend against taking the revolver apart. I've had many revolvers brought to me in Zip-Loc bags, where the person that disassembled it couldn't get it back together again. There is really no need to do this unless you have a lot of dirt/dust/lint built up inside of the revolver. And as someone else brought up: without the proper tools, you can really butcher up the screws and make the revolver look "junky."
There is nothing wrong... If S&W made the tolerances so tight that you didn't hear a rattle, the revolver would start malfunctioning when you had a little build-up of powder residue/dirt/dust that naturally tends to cling to the same oil that you used to lubricate the revolver.
HAVE FUN WITH YOUR NEW REVOLVER!!!
Regards,
Mike
