A theoretical answer. Yes. Headspacing would be established by the extractor grasping the case rim and holding the primer against the breech face. This would be similar to shooting 380 in a 9mm, but due to greater pressures, you will have more skin in the game, literally.

 

Ah, right! A temporary brain-fart caused me to forget about that
"headspaces on the mouth of the case" situation.

A .40 cal barrel would do the trick though; correct?

 

Granted its a Glock but interesting none the less

 

Yes if it's a revolver.

 

Interesting video! Thanks for that ...

 

I have a Glock 20 and shoot .40 in it. No problems at all. It is headspacing of the extractor. It is accurate. The only difference I notice is the brass dont fly out as far.

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Yes and no. Be warned that if you have hot loaded 40S&W Ammo ( or compromised brass ), you can potentially blowout the back of the case wall where it is not supported. I have had full 10mm do this in my competition days in my 1911 10mm race guns from compromised brass. It is not fun.