Those are some bad signs of high pressure spikes. Pierced primers aren't fun to deal with, especially in factory ammo.
Considering you weren't shooting a hell of a lot its not fouling in the barrel so that leaves a few things like headspace, cylinder end shake, firing pin etching, and ammo issues.
If you still have the 629, do some testing, unload the gun obviously
Place the empty cylinder in to battery and cock the hammer while you let your thumb drag along the cylinder until the hammer comes to full cock. Did the cylinder drop into the next slot easily just before the hammer stoped at full cock? If no, you have a timing issue.
Second, while the cylinder is in battery is there excessive back and forth movement on the cylinder if you try to push or pull with your fingers? If its more than just a very small amount you may have cylinder endshake.
Third is headspacing, this isnt easily done without go, no-go gauges that are reliable and calipers so leave that to S&W unless you feel you need to check it yourself, but for such a new firearm shouldnt be a problem.
Finally, firing pin etching is due primarily to overpressure ammo or badly seated primers that leak gases when struck. If this is the same ammo you were using before when the the gun broke last time dont shoot it and get rid of it. Or better yet, send the suspected ammo and casings with the gun for S&W to test.
That's the best I can tell you at the moment, hopefully your troubles get resolved quickly. Bird-dog the hell out of Smith and Wesson, this is unacceptable (IMHO) for such an established and respected gun-maker.
I'm already surrounded by half-dead brainless people already, the zombie apocalypse would just give me a reason to be productive and get rid of them.
Last edited by Ruzai; 02-09-2011 at 08:40 AM.