Can a 9mm bullet work in a .380 gun?
9mm and 380 both use bullets with a diameter of .355. However,
the cases are a different size. .380 is also known as .380 auto,
9mm Kurtz, 9mm Corto, 9mm short or 9x17. 9mm typically refers to
9x19mm also known as 9mm Parabellum or 9mm Luger.
You cannot fire a 9mm Parabellum cartridge from a .380 handgun.
The 9mm cartridge will not fit into the chamber of the gun.
However, if you were to pull the bullet out of the .380 case and
put it into a 9mm Para case the resulting cartridge will work just
fine.