Round not consistently extracting

[mestguy182]

Originally Posted by mrerick

The brass is "springy" and slightly malleable because it's job is to be pressed against the chamber wall and seal during firing the round.

The darkened area on one side of the brass is blow-by (blow-back) that is occurring because the brass is not sealing against the chamber wall evenly.

The Luger chamber (except for the very end of production in 1942) was made with an oblation ring - stepped chamber. The circular mark around the brass you see is from that step in the chamber.

Here's the drawing associated with Luger's patent on this:



Headspace is associated with the mouth to base cartridge measurement. The mouth rests on the right most step just prior to the leade into the barrel rifling. The breech face must be very close (thousandths of an inch) to the case base when the pistol is in battery.

You'll also notice that the entire chamber is very slightly tapered, including the area between the oblation ring and the right end of the chamber.

You may be dealing with damage or wear or dirt clogging an area around or in front of or just behind the oblation ring.

This is awesome, thank you for the detail. I'm an engineer and love this stuff. I gave the chamber it's first real good cleaning with a brass brush in years so I'm hoping that may help the situation.