Obviously, not all plastics are alike. If they made a pistol frame out of the same plastic that peanuts come in, it should be nearly indestructible. But I couldn't tell you anything about the plastics themselves no more than I could tell you anything about the finish that Glock uses on the slides. Speaking on behalf of Glock, I'd say one of the reason it is such a popular pistol is because even though it isn't stainless, the finish on the metal parts seems very durable. Perhaps people assume all guns are like that. It usually isn't mentioned when Glocks are discussed. But it happens to be less expensive than other pistols of equal quality, mostly.
How common is casehead failure in a pistol cartridge anyway, assuming it's a new factory round? While I realize that it is possible to blow up a handgun, all the ones on display that were blown up are made of steel--but the ammunition probably wasn't factory ammo.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.