380 cases split

I’ve seen it happen on any pistol brass that has a lot of mileage

Classic work hardening of the material. Probably has more to do with the brand of brass you started with, and its alloy. Follow that with the brand of dies you use, which determines how much cold working takes place. Then, whether you lube your brass.

Not all brass is created equal. Some brands are more thin at the mouth than others. I find this more on 380 brass.

What he^^^^ said.
Good eye.
It happens, but good reloaders catch it before it causes any problems.

I haven't noticed any more split necks on my 380 than on my 9MM but I load it and shoot it much less as well. 380 is probably my least loaded of my auto pistol ammo. I find many more of my 38 SPL brass with splits but they have been reloaded more than 100 times at least.

In my experience, .380 cases are more fragile than 9mm (at least they buckle more easily). Higher velocity (which isn't very fast in a .380) equals higher pressure, and it doesn't take a lot to get there quickly.

I use Win cases almost exclusively, and I've not had any splits, but I'm like most and don't shoot .380 as much as other calibers.

What pistol, what bullet, and what powder?

I load a fair bit of 380. Never seen a split. I have seen a few in 9mm though. No real rhyme or reason to it. I figure either the case had been fired many times, or simply a bad batch of brass.

Most of my brass is range pick-ups, so I have no idea of its history.

Another thought; unless your gun is newly manufactured, many European and "surplus" 380 ACP (9x17, 9mm Browning, 9mm Corto, 9mm Browning Court, etc.) have "generous" chambers which also add to the work hardening of the cases. Extra "work" sizing brass shot in larger chambers. But I've only been reloading 380 Auto for a SCCY for about 5 years and haven't found any splits, yet...

mdi said:

Another thought; unless your gun is newly manufactured, many European and "surplus" 380 ACP (9x17, 9mm Browning, 9mm Corto, 9mm Browning Court, etc.) have "generous" chambers which also add to the work hardening of the cases. Extra "work" sizing brass shot in larger chambers. But I've only been reloading 380 Auto for a SCCY for about 5 years and haven't found any splits, yet...

Click to expand...

Uh oh - rfwobbly won’t be happy hearing slander about European craftsmanship!

"It" happens on 380 brass, They are pretty thin. They crush easy if off center in the sizing die as well!