I've heard reports, from guys in and around the London trade, of guns passing proof at as little as .014". These would certainly be prone to denting easily, but would not be at risk of "blowing up". If they did, it would be do some sort of obstruction in the muzzle. With a muzzle obstruction, somethings going to give anyway. I'd rather that be as far from my face and hands as possible.
Jim