As described, your situation -- while not unheard of -- is incredibly uncommon. Five tries to fix an issue and now attempting a sixth is downright odd, frankly, because if S&W has confirmed there's an issue but can't run it down and get it right pretty quickly, they lose more time and money paying shipping and setting workers one problem gun this many times versus scrapping it and offering you a replacement or credit.

Did you buy your Model 60 new?

I don't think you're unreasonable wanting to wash your hands of this problem and expecting S&W to make you whole -- from your telling, you've offered more than every chance.

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Pickpocket