27 man, Not safe to shoot, not repairable, and a wall hanger as is. If S&W warranties it, I suspect they would just replace the gun. I've seen photos of the cracked alloy frames, and tend to examine my 642 more often than in past. That area beneath the barrel is super thin. I'm surprised it holds up as well as it does. My perspective on alloy frames in general, is that I accept the fact that they may not be as durable as steel, in exchange for their lighter weight. My 642 has not cracked.........yet. But my Alloy framed Colt Commander cracked after only moderate use with standard pressure ammo........ymmv

FWIW, I have occasionally dealt with S&W, for both warranty and paid work, over a lot of years. I don't know what their current attitude might be, but they have routinely gone above and beyond for me.

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NRA Life, COTEP 640