I thought I had seen something about this before in the forum but a search didn't yield what I was looking for. I am asking about the automatics. Can you shoot 380 bullets out of a 9mm. Thanks

No. They headspace on the case mouth, and the cases are different lengths. Also the .380 would almost certainly not cycle any 9mm in decent condition.

I won't say it's never worked, but it shouldn't and isn't a good idea.

Nope, the 380 auto cartridge and the 9mm Luger cartridge are different, and work at different pressures- not interchangeable at all.
I bet I know the source of your confusion, though. The diameter of the bullet (not the cartridge, just the projectile) is the same, at about .355. So, someone who reloads could load the same bullet into 380 cartridges and 9mm Luer cartridges.
Usually, the 9mm Luger uses heavier bullets than the 380, but they are the same diameter.

This is a trick question. the .380 cartridges sold in the USA are also known as 9mm Kurtz in Europe. These cartridges are identical. The 9mm Parabellum/9mm Luger cartridges are quite different. Do Not even try to mix these two different cartridges.

LLS