i'm not as much of an expert on ammo as some in this forum, but from my experience, it's the ammo.
i have tried that blazer ammo in my .357 mag. (it was all they had at that store and i was on my way to go shooting and didn't want to show up with no ammo at all) and although it didn't do what you experienced, i could see that happening with those cheapo casings.
i have had shell casings totally disintegrate before in my .22lr semi auto pistol. it was that winchester stuff that comes in the red plastic box. in the single magazine full that i fired, every second or third round the casing would disintegrate and cause the gun to jam pretty bad.
so, there's at least two kinds of factory ammo that i now know to avoid.
blazer .357 mag. and winchester .22lr.