I was standing there (Andre Norton Space Trader lingo, standing there, landing there, rumor range) for a rare double KaBoom, same stage of an IDPA match, consecutive or only one shooter between.
First the G21 .45. The casehead blew out, the magazine ejected but did not gang fire, the gun did not grenade.
Then the G22 .40. The casehead blew out, the extractor departed for parts unknown, the magazine ejected but did not gang fire, the gun did not grenade.
Loads were conservative, below maximum IDPA power floor loadings. There was no loud blast or hard kick to indicate an overload. Both previous bullets hit the target so there was no bore obstruction.
Both guns were inspected and returned to service. The .40 needed a new extractor, spring, and plunger, I don't recall the .45 losing or ruining any parts.
Gotta figure bad brass. Everybody talks about the "unsupported chamber" of a Glock but they have not looked closely at an old time "throated" 1911 which can show an amazing amount of brass without coming apart.