Well, that's very interesting! No telling the cause. Won't likely ever know. Sometimes, stuff just happens. But I still agree that it stinks that the factory gave you the cold shoulder about the repair! I have a 642 made in 2012 that had at least one previous owner. I'm pretty sure his middle name was Bubba and he carried this one in a metal tool box with loose tools! Has a dark spot in the barrel but no bulge because the location is underneath the portion covered by the frame that holds the forcing cone area of the barrel. Was test fired by the LGS (their standard policy on every used gun they sell) and inspected by their in house gunsmith that I have known personally for many years. I bought a box of +p ammo and he let me fire five cylinders full of that ammo into his bullet trap. The barrel and frame were not cracked to begin with and have not cracked to date after a good bit of firing. The gun shoots as good as any other of my J frames. Because of it's issues and it's sad exterior looks, it had sat in their case for long. I decided to take a chance on it and offered a very low price. I finally bought it for what I offered and another $25, total was very low! Been shooting and carrying it ever since I bought it in 2015. It's in my front pocket right now. I said that to say this, my copy has definitely been used and probably pretty roughly. I'd think if most hammer studs on most 642's were breaking within four years of normal usage, we'd know about it.

Rotten luck for you with yours, and worse that S&W didn't stand behind it for you! I assume the factory fixed yours for you and charged you for it or is it still busted or fixed by someone else? Just curious.

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So long ... Ken