I'm familiar with the one incident that spawned this urban myth. It involved a handloader trying to make a .40S&W hit the max pressure of the .10mm Auto. I belive that there was a "budget" after market barrel involved as well, possibly in an attempt to convert a 9mm to .40SW, but I'm not as possitive of that part of the incident. It has never been mentioned, but I also would not be suprised if there was a barrel obstruction that was never detected. In any case, the overpressure is confirmed, and there has only been that one confirmed and documented case.

The incident was seized on by a couple of radical 1911 fanatics. You know, the kind of pinheads who say that 9mm will bounce right off your chest, and that polymer frames are the same thing as tupperware. I wouldn't be at all suprised if it was then further promigulated by anti-gun activists working within the gun forum (and they are there). If the .40 Glock was unsafe, Glock would have recalled them all long before now. It is by far the most common sidearm in US federal law enforcement service, and that testing is just flat out abuse, much tougher than what the DOD requires. Why do you think that the Sig, which the DOD rates as equal to the Beretta 92, was the defacto standard DoJ and DoTr sidearm from the mid 80s until just a few years ago, when the vast majority of them were phased out by .40 caliber Glocks. Some lousy ammo choices with some of those agencies (the FBI subsonic 9mm debacle), but the weapons they pick are utterly reliable and safe, much more so than DoD selected items.