I can't speak for the older Lugers, but I have a 41 42 with British proofs. It survived a test round of 15 tons p/s/i (33,600 p/s/i)!

Well, if you want to retest a 1917 luger, here's the proof rounds :)

And alongside some military issue 9mm from january, 1917.

Hi Vlim, Will you provide the gun as well as the test rounds? Regards

Sure,

This old bugger should do. All the bits are 1917 :)

Thank you, sir.

The number on the side plate is 37. All other components are numbered 40.

The solution to the problem.
 

My gun was doing the same thing. Upon investigation I found the the trigger lever was not pushing the plunger in on the sear back when it jacked in the next round. Instead it was over-riding the plunger and causing the sear to disengage just as the bolt cloesed up on the second round.
I removed the flat spring and sear bar. I then removed the pin from the sear bar that holds in the plunger and spring.
The inside of the plunger hole was clean but the spring was very stiff. Actually the spring was too stiff.
So instead of the trigger lever pushing the plunger in - it was riding over the top of it and disengaging the sear. The plunger is supposed to push in when the bolt returns to battery. When you release the trigger the plunger pops out and the gun can be fired again.
I chose a weaker spring of the same diameter and trimmed it to length. I made sure the plunger worked in and out easily. It doesn't have to have much pressure - just enough to push the plunger out when you release the trigger.
Put it back together and all is well.

Thought this migh put things into to perspective of how and what that little plunger does.

Mike

I can't thank you enough, Mike. Awesome explanation of your problem and how you fixed it.

After getting all of the very helpful information from the Forum, and speaking with several folks, I've decided to field strip the Luger, give it a thorough cleaning, and then put it up for display after a light coat of protective oil. As many of the Forum contributors have written, it is almost 100 years old, and it's not worth stressing the metal/mechanics of the pistol. I'm gong to keep it in as pristine a condition as I can, and then pass it down to my only son. Hopefully, he will have an appreciation of its historical value, and the sentimental value that it has been in the family since his great-uncle brought it home from the war.

Again, many thanks to all who have contributed to my original thread.

If still looking for a gunmaster in the local area.....

http://laroccagunworks.com/

That's very unusual on pistol cartridge.

Q1: Was it because that DWM did not know fast burning being important in the early stage of auto pistol cartridge design, or was it because they had other concerns or considerations?

Q2: Was slow burning powder unique on DWM 487C (?), or universal on their other pistol cartridges of that era?

TIA

Thanks, Alvin. Yes, I've spoken with Mike Larocca a couple of times over the phone. He seems like a very knowledgeable individual and his experience is quite impressive. I'm going to try to get out to see him one of these days. Thanks for taking the time to write me.