Hand raised.
My very first handgun was a brand new S&W M19-6. The forcing cone gave up the ghost with a 158 grain JHP factory load (I wanna say it was a Remington), about 6 months into my ownership. S&W promptly fixed it and returned it to me post-paid.
While gunsmithing at a S&W warranty depot, I saw split forcing cones fairly frequently. But keep in mind, these were almost always LE guns. I would also add that it is my opinion that the issue was not due to light bullets, as I have seen many that were split with heavier bullets; as was mine. It should also be noted that the issue did crop up on rare occasion with K frame .38 Specials; again, almost always LE guns.
The new M66’s are MUCH tougher revolvers and S&W no longer recommends limiting the use of magnum loads.
