Gass relief hole botom of breech block.

[DonVoigt]

Sorry Seiger,
I did not "assume" the primers were brittle- the OP stated someone "else" said that, I was only questioning why the temperature of the pistol would matter- If this were true.
Personally I don't buy the brittle primer story---


The mention of today's Fiocchi is relevant to the idea or desire to add the relief hole to a pistol for shooting today that does not have one- as the OP mentioned.

I have posted photos of the "holey" Fiocchi primers, and of the added gas relieve hole- these are readily verifiable. It is clear that the added hole gives gas a place to exit the bolt, which does not exist in the original design.

It is gratifying to note that now we all seem to be in agreement that the commonly seen fluting does absolutely nothing to allow gas escape. The Swiss and Mauser mods, may give a little improvement- but I have not studied them; since I have neither "brand" luger.
Perhaps this often repeated, but wrong, tale will die now, or soon.

Now please explain why you even mentioned the temperature of the pistol metal?