If the neck WAS too long it would extend beyond the chamber headspace and as the cartridge is fired the cartridge mouth would be pressed into the actual barrel..pinning it in place. Could make it difficult to extract.

A bottleneck cartridge should headspace on the shoulder. The SAAMI spec I pointed to earlier shows this measured to the middle of the bottleneck shoulder.

It might be that someone took a 9mm reamer to the normally tapered chamber of a .30 Luger chamber... The chamber should be .3918 inches where the thick web of the case ends and .3805 at the start of the shoulder.

I'm only speculating without a cast of the chamber or good photos.

Could be most anything, including a simple defective case.

100% agree. No need to overthink it.

Nothing wrong with thinking it either. I have lost track but I don't believe we have ever been able to see the base of this cartridge. That would be a helpful clue to determine if over pressure was a factor.
A careful analysis of a problem like this seems prudent to me.

http://forum.lugerforum.com/showpost...5&postcount=13

Or do we need to also see the head of the case?

Maybe it helps to go back and read the original post,
two rounds fired ok, then switch of ammo and the separated case was discovered.

Perhaps 4scale will come back an add a little more to answer some of the questions posed;
like is it really a .30 luger? Does it shoot ok with Privi ammo?

OK,,very confusing thread..4 scale is the original poster with a sheared case..then ttarp shows a case with the base present in post #13 THIS case looks like it fired out of battery. Or at least with the case partially out of the chamber?
4 scale says he was unable to find the base of his sheared cartridge?

Yes Jerry it is bit of a confusing thread with two separate collectors showing a similar malfunction.

I've long since disposed of the sheared case so I'm unable to examine the shoulder. The shoulder of the sheared round does look long in the photo in post #1. As I recall it did take a good shove to drive the sheared case out of the chamber, so I'm wondering if maybe Jerry is right in his post #21 that the long neck is the culprit.

The pistol used to fire the sheared round shown in post #1 of the thread was a Portuguese 1906 with the royal crest scrubbed off. It has performed flawlessly with perhaps 100 rounds of .30 Luger Prvi Partizan ammo since the sheared case. I have verified the pistol is chambered for .30 Luger (a 9mm Luger dummy round will not chamber). After considering all comments I believe it was just the one defective round. But, next range trip I'll save some ejected cases and compare to unfired ammo to see if something is going on.

I'm sorry for the confusion, I should have started a new thread.

At any rate, after a good cleaning, went back to the range and fired about half a box of PPU, and then went on to finish up the box Fiocchi without issue.

Thanks for everyone's help, and I'm sorry again for the confusion.