This question applies to any 9mm handgun really, but the only 9mm I have currently is a Glock 17.

In an emergency situation, could you fire a .380 round from a 9mm Glock?  Would it damage the bbl?  Would it be accurate?  Would the weapon cycle?

Just curious and not willing to try it in person!

I had a buddy of mine shoot .380 rounds out of a S&W .9mm once. He was at the range and got .380 ammo mixed in with his .9mm ammo. The .380 ammo would chamber and fire, but it would not cycle the action. The .380 bullet is the same diameter as the .9mm, it just has a shorter case.

www.chuckhawks.com/380ACP.htm

As for accuracy, I have no idea as he was shooting both types of ammo on a combat style course and when we discovered why his weapon was not functioning all of the time, we removed the .380 from the range.

Quoted: In an emergency situation, could you fire a .380 round from a 9mm Glock?

Yes

Quoted: Would it damage the bbl?

No

Quoted: Would it be accurate?

Yes

Quoted: Would the weapon cycle?

No, it would reduce the weapon to a single shot. The 380 Glocks are a semi-blow back with a special cut slide and barrel hood.
At one time Jarvis or Barsto was experimenting with a barrel but dropped the project because it would not function correctly.

Here's an idea...have enough 9mm ammo on hand for emergencies!

I've heard alot of "preparedness" scenarios over the years and NONE of them have taken into consideration firing the wrong round through any given firearm.

Besides, in an "emergency" I bet you'll be able to find 9mm ammo easier than any other caliber, including .380...

Right, I was just curious.

Technically it is still a 9mm bullet, so I was mainly curious about the weapon cycling and the pressures of the smaller cartridge.