I pulled out my dads ruger security six yesterday and the cases bounch a little bit back and forth inside the cyclinders. I didn't inspect it close enough to tell if the round inline with bore moved at all. I know that that is the only place that the headspacing counts, but at first impression it seemed a bit unnerving. The cylinders themselves all seem to be good fit though

It sounds like an issue with too much crimp rather than headspacing. Since most revolver cartridges reference off the base of the case headspacing is a non issue. That said, on my 44 mag, I crimp them so they just slide in easily. To little and I have to push them in, too much and they rattle, but just the slightest bit. They shoot fine, I wouldn't worry.

It sounds like an issue with too much crimp rather than headspacing. Since most revolver cartridges reference off the base of the case headspacing is a non issue. That said, on my 44 mag, I crimp them so they just slide in easily. To little and I have to push them in, too much and they rattle, but just the slightest bit. They shoot fine, I wouldn't worry.

These are factory cases. I haven't reloaded any 357 yet

Then no issue. Shoot em.

Completely agree with Chris, shouldn't have any problems....shoot away.

I have a ruger single six in 22mag with the 8 1/2 barrel and they rattle like crazy, back and forth side to side, but it shoots perfect and the cases just fall out when done. :D
Just go shoot it.