You do realize why this is totally different than shooting a .380 out of a 9mm.
The case diameter of a .40 is significantly larger than a 9. A 9mm case will expand to fill the volume. If it stretches and tears, you have a problem.
A .380 case is nominally the same diameter as a 9mm. So the only diameter that does not the same is length. Since the bullet is designed to release the gasses out the front of the case, this isn't a problem.
Again, if you understand the difference between the calibers, you would see that case failure is not an option. Either it works, or the round doesn't go off.
The case is actually BETTER supported than it is in a .380 because the excessive head space causes it to sit deeper in the chamber.
But if it makes anyone feel better I'll include this disclaimer:
Don't try this at home Kids.
If everyone followed your logic, no wildcat cartridges would ever exist.
I have tools that someone even 20 years ago could not have dreamed of. By using QuickLoad, I could model internal ballistics and was able to see that the very long jump resulted in very very low chamber pressures.