I won't go into why, but I have intentionally fired .380 ACP through both a 9mm Hi-Power and through a 1911 using both a 9mm barrel and a .38 Super barrel. It's a bit tough on the extractor because the case is "headspacing" (if we can still use that term) on the extractor hook, but aside from that it worked.
I don't make a practice of it. It was done in the pursuit of a very specific investigation I was involved in at the time.
I don't think it's unsafe, but I don't recommend it.