Another possible bit of information was contained in the thread "Makarov Pistol: 380 vs 9x19mm". It had to do with physical comparisons of 380, 9x18 and 9x19. In summary, the facts submitted by various writers were:
380: Other designations: 9x17, 9mm Kurz, 9mm short
Size (Diameter): 0.355" dia.
Bullet: Uses regular 9mm bullet
9x18: Other designations: 9mm Makarov
Size: 0.365" dia.
Bullet: Does NOT use the regular 9mm bullet
9x19 Other designations: Luger,Parabellum (This is the regular 9mm)
Diameter: 0.355" dia.
Bullet: Uses regular 9mm bullet
The 9x18 is less common than the other two. Again, the "regular" 9mm is
the 9x19.