I had an 042 that had the same crack; S&W sent a new no lock 442 and took care of it, but it wasn't the same so I sold it off. I have a 642-1 as well, and it has no sign of it. I thought it was because of overtorqueing the barrel, but apparently it can occur just from regular shooting. Kinda disturbing; it's my most carried gun BY FAR.

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MARK