Just an FYI - this is a Zombie thread from 2009.

I'm pretty sure the OP either got his answer from Smith or not.

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As far as I can recall, flame cutting only proved to be a problem on a very small number of steel frame revolvers chambered in calibers like .357 Maximum.

Otherwise as noted above, in a steel frame revolver, flame cutting is a self limiting process that stops before it weakens the top strap to any significant degree.