I won't get into the choice-of-verbage controversy but I admit I was a little confused about the details of the incident after reading the initial post. I was curious why the gun was fired after the OP had detected something about the gun (I am still not sure what) that gave him pause. But, anyway, the main thing is I'm glad to know you weren't seriously injured!

I happen to see a 640 fracture and eject a barrel just like the second gun - without apparent damage to the frame. It was about a year or so ago (I think?) and the shooter was actually unaware of the failure. We had to go out and stop him from shooting again. Don't ask me what he thought he was using for a front sight!

The question about the ultra-sonic cleaner is a good one, but it seems more likely the guns were defective in either design, manufacturing, or assembly. The gun I saw fail was a used gun that was fired a few times and traded back to the selling dealer within a couple weeks of purchase. It was being test-fired by a prospective customer when it failed. That gun probably was not one likely to have received extraordinary cleaning. S&W, to their credit, repaired the gun at no charge to the dealer.

While I agree that things happen, and sometimes it is best not to make too much of them, I certainly would ask for a different model too! Enough is enough. You know what they say about the third strike!