[Double Tap]

The head diameter of the .380 is smaller than the 9mmP, so firing a .380 in a 9mmP chamber could cause a case rupture and damage to the gun and your hand. It is also possible, though remote, that the .380 round could slip out from under the extractor and get pushed up into the chamber. Then if a 9mmP round were chambered behind it and it had a FMJ bullet it could conceivably set off the .380 round with the slide out of battery. This would also cause gun damage and possibly injury.

[JRandomFreeper]

so firing a .380 in a 9mmP chamber could cause a case rupture and damage to the gun and your hand.

You quote from the range officer that chewed me out. I did luck out. I always check ammo now. Always.

/john

[TXnMA]

The head diameter of the .380 is smaller than the 9mmP,

The (rimless, in both cases) head of the .380/9mmKurtz/9mm short/9X17 case is definitely smaller than that of the full-sized 9mmParabellum/9X19 case.

In fact, here is a useful bit of trivia: the base of the .380 pistol round and the .223/5.56mm rifle round are basically the same -- they use the same baseplate for reloading.

How does that make you M-16/AR-15 fans feel -- to recognize that your rifle's case diameter is the same as the relatively puny .380 pistol cartridge...? ;-}

[Dave S]

firing a .380 in a 9mmP chamber could cause a case rupture and damage to the gun and your hand.

Oops. I wont be doing that then. My hand thanks you.