The few guns I've seen, that have "let go", generally the charge seems to be directed up, back and/or, to the sides. Usually the mag will get blown clear of the gun, too. If there's sufficient pressure directed through the handle, (which I suppose could happen - though I've not seen it) - aluminum would have the best chance of containing it. There's a lot of variables though - the construction of the gun, the materials used, etc. If it's a real concern, rather than just a curiosity - stick with a steel frame gun. My buddy use to work for the Eastern Canada importer for Glocks and a couple of those came back, after a "catastrophic failure" - glad I wasn't holding onto it when it happened. Ever see what happens to a 'Vette, when it hits a hydro pole, or bridge abutment ? That's what it reminded me of.