9mm brass with serrations

[wv109323]

I picked up some 9mm brass after a local USPSA match. Some of the brass has vertical serrations on it. It reminds of .308 brass fired in a H&K rifle. The serrations are not very deep and almost undectable by feeling the case. The noticeable lines are from the escaping gas that causes a dark lines down the brass.
My question Is there a pistol or pistol caliber carbine that uses a fluted chamber? Or could it be caused by roll sizing the brass? This was reloaded cases.
Just curious as I have never seen this before on 9mm brass. Any percautions about reloading the brass?

[Der Gebirgsjager]

No problems with reloading it, as there is none with brass from HK rifles. What made it on 9mm is a mystery to me also, but a wild guess, could it be an HK submachine gun like the MP-5?

DG

[kevin c]

USPSA has a Pistol Caliber Carbine Division, where the dominant chambering is 9 x 19. Lots of fluted chambers, blow back actions and soft loads (pushing a 124 grain slug at just over 1000 fps passes muster) means dirty pinstriped brass is very common. I personally don’t reload it, but others don’t seem to mind (maybe no 9 major type loads , though).

The case mouth on such brass isn’t different that I know of; the marks are all on the case exterior: soot from lack of obturation and, as the OP described, maybe some marks from the fluting.

[atfsux]

HK made more than a few designs with fluted chambers. The MP-5/HK-94 series is the most likely, but even the P-7 "squeeze-cocker" handgun also has this.

[wv109323]

Kevin C, your answer makes since. There was a competitor with a PCC in 9MM. I did not know anyone fluted the chambers though. The serrations extend about 2/3 down the case. I resized some of the cases and the resizing removes all serrations.