If it had been a .22lr then no problem, they're made to fire stingersBest "blow up" I've seen was a .270 barrel that hadn't been shot for two weeks. Left in a slip inside a gun room in October in Northumbria after cleaning.
When next fired it bulged and split about eight inches from the crown.
Turned out a wasp had used it to overwinter. The cocoon it spun was enough to provide a seal with the bullet.
Now, we all know to check the barrel is clear but not many do it on a dark morning.