[chickenfried]

Hi guys,
Shot my CZ-75B using S&B 9mm FMJ ammo, new gun around 200 rounds fired. Noticed something weird with the spent brass. On about half the brass on one side, there's an area near the mouth that's ?scorched? black, the areas about the size of a 9mm bullet? Scorching doesn't wipe clean, but can be scraped off. Even on the brass without the black marks, you can see slight discoloration where the black marks would've been. Is this normal or a sign of something wrong? Brass is not bulged or misshapen in anyway. I'm currently having computer problems, no internet connection. So please excuse me if it takes me a while to respond to your postings. Thanks.

[stans]

Scorch marks on the brass near the case mouth usually indicate that the brass is not making a good seal against the chamber wall during firing. This could be the result of a chamber that is not exactly round, overly hard brass that will not form itself to the chamber wall, or the operating pressure of the round is low enough that the brass does not expand enough to seal the chamber.

[Haycreek]

The "scorched brass" doesn't hurt anything, and the tumbler will clean it. I may not know what causes the scorched brass, but I always thought that it may have something to do with the "load" and/or the speed of the powder used. Others may have a better answer. :)

[HSMITH]

That S&B brass is as hard as woodpecker lips, and thick. Depending on the particular loading you had this very well could be a completely normal thing. Try a few other brands of ammo and see what they are like after you scrub the chamber out well. While doing this bear in mind that lower pressure or slower to peak pressure loads will have soot on the brass no matter what the gun is, but normal full power 9mm loads should not show much soot tracking down the side of the brass. Personally I would not worry much about it as long as the gun is reliable and accurate.

[J.M.]

Stans and HSMITH nailed it - try a different brand of ammo just to be sure it's not an issue with your chamber, but don't worry about it.

[mete]

Yes it's just gas escaping around the case. I guess you've never seen a case from a HK P7, the fluted chamber leaves a series of soot marks where the flutes were !

[chickenfried]

Thanks for the info, guys.